Tornado and Flash Flooding in Iowa, August 10 to 12, 2010

Name: Tornado and Flash Flooding in Iowa, August 10 to 12, 2010
Start: 2010-08-10T14:57
End: 2010-08-12T01:30
Location: Iowa

August 10 to 12, 2010 · NWS DMX · 64 events in 19 counties and zones

Once again the atmosphere over Iowa became very unstable during the peak heating of the day. CAPE rose to 3500-4500 J/kg by the mid to late afternoon with lifted indices of -8 to -10 C.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 1
Injuries: 4
Property damage: $52 million
Crop damage: $135,000
Events: 64

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS DMX wrote it up.

Once again the atmosphere over Iowa became very unstable during the peak heating of the day. CAPE rose to 3500-4500 J/kg by the mid to late afternoon with lifted indices of -8 to -10 C. The moisture pooled over the state with precipitable water values approaching 2 inches by evening. High temperatures reached the upper 80s to low 90s, with dewpoints topping out in the upper 70s to low 80s. The atmosphere was fairly weakly sheared with 30 kts of available shear. Downdraft CAPE was between 1000 and 1800 J/kg. Available CAPE in the -10 to -30 C layer of the atmosphere was 800-1100 J/kg, but hail was limited by the high freezing level, 16,000 to 16,500 feet. Quarter size hail fell in Calhoun County as an intense storm passed though. The same storm cluster produced a funnel cloud in Sac County earlier. Scattered winds occurred with the storms. A 61 MPH wind gust was recorded in Eagle Grove for example and windows were blown out in Humboldt County south of Thor. One of the thunderstorms produced a tornado in Emmet County. The tornado touched down briefly over Lake Iowa. Thunderstorms became more organized during the evening and produced very heavy rainfall. In addition to the rainfall, scattered reports of high winds and some hail up to an inch and one quarter in size were received. Most of the wind reports were around 60 MPH. By far the most significant weather was the heavy rainfall. Three to 5 inches of rain fell on saturated ground, resulting in a very widespread flash flood event. Nearly half of the CWA was involved from parts of north central Iowa south to the Missouri border. Numerous roads were covered with flowing water of 1 to 2 feet in depth. Lightning struck a car at mile post 105 on Interstate 35 in Story County. No injuries were reported. Lightning also struck a house in Ankeny, causing a fire. The flash flooding claimed one life in central Iowa. Three vehicles were swept into the waters of Mud Creek near Altoona in Polk County. There were 11 people involved. A rescue call was made to save the occupants of the cars. One 16 year old female perished in the flood waters, the other 10 were rescued, though 4 were injured and received treatment at a local hospital. The flash flooding transitioned into widespread flooding as the night progressed into the day of the 11th. Flash flooding resulted in evacuations of apartments and trailer courts on the east side of Des Moines. Interstate 35 was covered by water due to flash flooding at mile post 97. Several cars spun out in the flood waters. Very intense rainfall in the Ames area resulted in a record crest on Squaw Creek. The creek crested 1.5 to 2.5 feet above the record high stage. Major flooding took place and the water treatment plant was inundated. Major damage was done to several buildings on the Iowa State Campus. Damage to Iowa State alone was between $40,000,000 and $50,000,000. Flooding from the Skunk River closed U.S. Highway 30. Thirty people were rescued at a Wal-Mart store in Ames as well. Following the severe flooding, several Iowa counties were added to the Presidential Disaster Declaration number 1930. The original 32 were: Adams, Appanoose, Audubon, Buena Vista, Butler, Cherokee, Clay, Davis, Decatur, Franklin, Howard, Humboldt, Iowa, Lee, Lyon, Madison, Marion, Mills, Monroe, Montgomery, O Brien, Osceola, Palo Alto, Ringgold, Shelby, Union, Van Buren, Wapello, Warren, Wayne, Webster and Wright. Eighteen were added to the original, incuding: Black Hawk, Boone, Buchanan, Clayton, Delaware, Dickinson, Dubuque, Emmet, Fayette, Guthrie, Jackson, Jasper, Jones, Lucas, Mahaska, Polk, Sioux and Story. In addition, Governor Chet Culver had issued disaster proclamations for 50 Iowa counties due to inclement weather since June 1, 2010: Appanoose, Black Hawk, Boone, Buchanan, Buena Vista, Butler, Cherokee, Clay, Clayton, Davis, Decatur, Delaware, Dickinson, Dubuque, Emmet, Fayette, Franklin, Hamilton, Hancock, Howard, Humboldt, Jackson, Jasper, Jefferson, Johnson, Jones, Kossuth, Lee, Lucas, Lyon, Mahaska, Marion, Monona, Monroe, O'Brien, Osceola, Palo Alto, Polk, Ringgold, Shelby, Sioux, Story, Taylor, Union, Van Buren, Wapello, Warren, Washington, Webster and Wright.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Des Moines, IA wrote its last area forecast discussion before the first event at Aug 10, 2:48 PM CST, 9 minutes earlier.

Area forecast discussion, Aug 10, 2:48 PM CST, 9 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
348 PM CDT TUE AUG 10 2010

.SHORT TERM /TONIGHT/...
CONVECTION CURRENTLY ONGOING ACROSS WESTERN IOWA IS EXPECTED TO
MAINTAIN ITSELF THROUGH THIS EVENING AND THEN BECOME MORE WIDESPREAD
OVERNIGHT AS LOW LEVEL JET INCREASES. EARLIER TODAY AN OUTFLOW
BOUNDARY ORIENTED EAST/WEST STALLED OVER CENTRAL IOWA AND IS STILL
EVIDENT BY THE SUBTLE WIND SHIFT FROM SOUTHERLIES SOUTH OF THE
BOUNDARY TO MORE EASTERLY NORTH OF THE BOUNDARY. GIVEN THE RECENT
HEAVY RAINS AND PRECIPITABLE WATER AMOUNTS IN EXCESS OF 2
INCHES...HAVE ISSUED FLASH FLOOD WATCH CENTERED AROUND CENTRAL CWA.
LOCALIZED RAINFALL RATES OF 1 TO 2 INCHES ARE LIKELY...WHICH WOULD
CAUSE ADDITIONAL HYDRO PROBLEMS TO THESE AREAS. ISOLATED SEVERE
THREAT CAN NOT BE RULED OUT GIVEN THE LARGE CAPE VALUES.

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
VERY COMPLEX AND BUSY FORECAST OVER THE NEXT SEVERAL DAYS WITH A
PLETHORA OF HAZARDS TO CONSIDER. HOT AND HUMID WEATHER WILL PERSIST
WITH MULTIPLE ROUNDS OF THUNDERSTORMS POSSIBLE...ESPECIALLY TONIGHT
AND THURSDAY NIGHT THROUGH FRIDAY...KEEPING HEAVY RAIN/FLOODING
POTENTIAL HIGH THROUGH THE END OF THE WORK WEEK. DID NOT MAKE MANY
CHANCES TO THIS FORECAST PERIOD BUT DID INCREASE DEWPOINTS A BIT
FURTHER AT TIMES OVER THE NEXT FEW DAYS. HAVE LEFT THE EXCESSIVE
HEAT WARNING FOR THE NEXT COUPLE OF DAYS UNTOUCHED AND EXPANDED THE
CORRESPONDING HEAT ADVISORY A BIT FURTHER NORTH INTO
WEBSTER...STORY...MARSHALL...AND TAMA COUNTIES. ALSO INCREASED POPS
FROM THURSDAY NIGHT THROUGH FRIDAY NIGHT WHEN IT APPEARS ANOTHER
SHORTWAVE WILL MOVE THROUGH FOLLOWED BY THE LONGER WAVE TROUGH AS
THE PARENT MID/UPPER LOW MOVES BY WELL TO OUR NORTH.
THEREAFTER...SOME RELIEF APPEARS IN STORE FROM THE WEEKEND INTO
EARLY NEXT WEEK AS WE ENTER A QUIETER WEST NORTHWEST/CYCLONIC
STEERING FLOW ALOFT AND ADVECT SOME COOLER AND DRIER LOW-LEVEL AIR
INTO THE AREA. KEPT FORECAST DRY FROM LATE SATURDAY
ONWARD...ALTHOUGH VARIOUS LONG RANGE MODELS TRY TO SPIT OUT LIGHT
QPFS AT TIMES.

&&

.AVIATION...10/18Z
LINE OF THUNDERSTORMS IN WESTERN IOWA IS SLOWLY WEAKENING...BUT HAVE
MENTION OF CB BY 22Z AT FOD TO ACCOUNT FOR THIS. THUNDERSTORM
REDEVELOPMENT IS EXPECTED LATER THIS AFTERNOON ACROSS WESTERN IOWA
AND WILL AFFECT ALL TAF SITES THROUGH THE OVER NIGHT HOURS AS THEY
MOVE EAST/SOUTHEAST. LOW CLOUDS/FOG WILL FOLLOW WITH MVFR CONDITIONS
BY EARLY TOMORROW MORNING. WOULD NOT BE SURPRISED IF A FEW LOCATIONS
EXPERIENCE IFR CONDITIONS AS INDICATED BY SCT005 GROUP...BUT
CONFIDENCE IN TIMING AND LOCATION IS LOW. GRADUALLY EXPECT
CONDITIONS TO IMPROVE AFTER 11/13Z.

THUNDERSTORMS AND MAINLY MVFR CONDITIONS WILL CONTINUE TO AFFECT
KFOD/KMCW/KALO THROUGH 14Z.  THIS WILL BE FOLLOWED BY HOT AND HUMID
VFR CONDITIONS THROUGHOUT MUCH OF THE DAY.  ADDITIONAL THUNDERSTORMS
MAY DEVELOP DURING PEAK HEATING AND CONTINUE OVERNIGHT...BUT
CONFIDENCE IN ANY PARTICULAR TIME OR LOCATION HAS PRECLUDED ANY
MENTION BEYOND CB WORDING FOR THE TIME BEING.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY UNTIL 7 PM CDT THURSDAY FOR
APPANOOSE-BOONE-CALHOUN-CLARKE-DALLAS-DAVIS-DECATUR-GREENE-JASPER-
LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-POLK-POWESHIEK-SAC-STORY
-TAMA-WAPELLO-WARREN-WAYNE-WEBSTER.

FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH WEDNESDAY
MORNING FOR BLACK HAWK-BOONE-BREMER-BUTLER-DALLAS-FRANKLIN-
GREENE-GRUNDY-HAMILTON-HARDIN-JASPER-MADISON-MAHASKA-MARION-
MARSHALL-POLK-POWESHIEK-STORY-TAMA-WARREN-WEBSTER.

EXCESSIVE HEAT WARNING UNTIL 7 PM CDT THURSDAY FOR ADAIR-ADAMS-
AUDUBON-CARROLL-CASS-CRAWFORD-GUTHRIE-RINGGOLD-TAYLOR-UNION.

&&

SHORT TERM...BEITLICH
LONG TERM...LEE
AVIATION...BEITLICH

Hazardous weather outlook, Aug 10, 5:14 AM CST, 9 hours 43 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
614 AM CDT TUE AUG 10 2010

IAZ044-045-057-058-070-071-081-082-092-093-111100-
CRAWFORD-CARROLL-AUDUBON-GUTHRIE-CASS-ADAIR-ADAMS-UNION-TAYLOR-
RINGGOLD-
614 AM CDT TUE AUG 10 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST IOWA.

.DAY ONE...TODAY AND TONIGHT

AN EXCESSIVE HEAT WARNING IS IN EFFECT TODAY AND TONIGHT WITH HEAT
INDICES APPROACHING 110 DURING PEAK HEATING OF THE AFTERNOON...AND
DROPPING NO LOWER THAN 75 TONIGHT.  PLEASE REFER TO THE NATIONAL
WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES FOR FURTHER
DETAILS.

THERE WILL BE CHANCES FOR THUNDERSTORMS AGAIN TONIGHT. SOME MAY
PRODUCE HEAVY RAINS AND POTENTIALLY FLOODING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

HEAT INDEX TEMPERATURES OF 110 DEGREES OR GREATER ARE EXPECTED WEDNESDAY
AND THURSDAY. AN EXCESSIVE HEAT WARNING REMAINS IN EFFECT THROUGH THURSDAY.
PLEASE REFER TO THE NATIONAL WEATHER SERVICE WEBSITE AT
WEATHER.GOV/DESMOINES FOR FURTHER DETAILS.

THUNDERSTORM CHANCES RETURN TO THE FORECAST THURSDAY NIGHT THROUGH
FRIDAY NIGHT. A FEW STORMS MAY BE SEVERE WITH ADDITIONAL POTENTIAL
FOR HEAVY RAINS AND FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THURSDAY OR FRIDAY.

IAZ033-034-046-047-059>062-072>075-083>086-094>097-111100-
SAC-CALHOUN-GREENE-BOONE-DALLAS-POLK-JASPER-POWESHIEK-MADISON-WARREN-
MARION-MAHASKA-CLARKE-LUCAS-MONROE-WAPELLO-DECATUR-WAYNE-APPANOOSE-
DAVIS-
614 AM CDT TUE AUG 10 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND SOUTHERN IOWA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORM CHANCES REMAIN IN THE FORECAST LATER TODAY AND AGAIN
TONIGHT. SOME OF THESE STORMS MAY PRODUCE HEAVY RAINS AND FLASH
FLOODING. A SEVERE STORM IS ALSO POSSIBLE.

A HEAT ADVISORY IS ALSO IN EFFECT FOR THE AREA. HEAT INDICES MAY
REACH OR EXCEED 105 DEGREES DURING THE PEAK HEATING OF THE
AFTERNOON...AND STAY AT 75 DEGREES OR MORE TONIGHT.  PLEASE REFER
TO THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES
FOR FURTHER DETAILS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

HEAT INDEX TEMPERATURES OF 105 DEGREES OR GREATER ARE EXPECTED
WEDNESDAY AND THURSDAY. A HEAT ADVISORY REMAINS IN EFFECT THROUGH
THURSDAY. PLEASE REFER TO THE NATIONAL WEATHER SERVICE WEBSITE AT
WEATHER.GOV/DESMOINES FOR FURTHER DETAILS.

THUNDERSTORM CHANCES RETURN TO THE FORECAST THURSDAY NIGHT THROUGH
FRIDAY NIGHT. A FEW STORMS MAY BE SEVERE WITH ADDITIONAL POTENTIAL
FOR HEAVY RAINS AND FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THURSDAY OR FRIDAY.

IAZ004>007-015>017-023>028-035>039-048>050-111100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-WEBSTER-HAMILTON-
HARDIN-GRUNDY-BLACK HAWK-STORY-MARSHALL-TAMA-
614 AM CDT TUE AUG 10 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHERN IOWA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORM CHANCES REMAIN IN THE FORECAST LATER TODAY AND AGAIN
TONIGHT. SOME OF THESE STORMS MAY PRODUCE HEAVY RAINS AND FLASH
FLOODING.  A SEVERE STORM IS ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

HEAT INDEX TEMPERATURES MAY APPROACH 105 DEGREES WEDNESDAY AND
THURSDAY. THUNDERSTORM CHANCES ALSO RETURN TO THE FORECAST
THURSDAY NIGHT THROUGH FRIDAY NIGHT. A FEW STORMS MAY BE SEVERE
WITH ADDITIONAL POTENTIAL FOR HEAVY RAINS AND FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THURSDAY OR FRIDAY.

SMALL

The radar

The Des Moines radar (KDMX), 128 km away, was scanning. The volume nearest the first event began at 20:58 UTC.

Open the radar archive at this moment

Event by event

31 flash flood, 16 heavy rain, 8 thunderstorm wind, 3 flood, 2 hail, 2 lightning, 1 funnel cloud, 1 tornado. Local standard time, as filed.

Funnel Cloud, Sac

When: August 10, 2:57 PM CST
Where: Sac County, 2.04 mi E of Sac City
Reported by: Law Enforcement
Coordinates: 42.420, -94.960

Heavy Rain, Webster

When: August 10, 4:00 PM CST to 7:30 PM CST
Where: Webster County, 2.81 mi N of Burnside
Reported by: Trained Spotter
Coordinates: 42.390, -94.110

Rainfall of 3.9 inches since 1600 CST.

Thunderstorm Wind, Humboldt

When: August 10, 4:44 PM CST
Where: Humboldt County, 1.38 mi S of Thor
Measured: 52 kt (60 mph) estimated gust
Property damage: $2,000
Reported by: Broadcast Media
Coordinates: 42.660, -94.050

Windows blown out by estimated winds of 60 MPH.

Tornado, Emmet

When: August 10, 4:44 PM CST to 4:45 PM CST
Where: Emmet County, 7.17 mi NNE of Armstrong to 7.33 mi NNE of Armstrong
Rating: EF0
Path length: 0.18 mi
Path width: 40 yd
Reported by: Emergency Manager
Coordinates: 43.498, -94.452

A tornado formed and touched down briefly over Iowa Lake.

Thunderstorm Wind, Wright

When: August 10, 4:56 PM CST
Where: Wright County, Eagle Grove
Measured: 53 kt (61 mph) measured gust
Property damage: $2,000
Reported by: Broadcast Media
Coordinates: 42.670, -93.900

Measured by a schoolnet site.

Heavy Rain, Calhoun

When: August 10, 5:00 PM CST
Where: Calhoun County, Pomeroy
Reported by: Law Enforcement
Coordinates: 42.550, -94.680

Calhoun County Law Enforcement reports streets in Pomeroy inundated as well as many county roads. Highway 4 in Pomeroy had standing water 2 feet deep in underpasses.

Heavy Rain, Webster

When: August 10, 5:00 PM CST to 8:15 PM CST
Where: Webster County, 1.23 mi NE of Lundgren
Reported by: Trained Spotter
Coordinates: 42.360, -94.150

Two and one half inches of rain since 1700 CST.

Hail, Calhoun

When: August 10, 5:15 PM CST
Where: Calhoun County, Rockwell City
Measured: 1 in hail
Property damage: $2,000
Reported by: Law Enforcement
Coordinates: 42.400, -94.630

Quarter size hail was reported at the police station.

Heavy Rain, Webster

When: August 10, 5:57 PM CST
Where: Webster County, 0.69 mi S of Callender
Reported by: Public
Coordinates: 42.360, -94.300

Public reports of standing water 2 feet deep surrounding homes in Callender, with additional water flowing from fields and yards.

Heavy Rain, Hamilton

When: August 10, 6:00 PM CST to August 11, 5:17 AM CST
Where: Hamilton County, 5.67 mi E of Randall
Reported by: Trained Spotter
Coordinates: 42.220, -93.490

Rainfall since Tuesday night was 5.2 inches.

Flash Flood, Webster

When: August 10, 6:50 PM CST to August 11, 12:00 AM CST
Where: Webster County, 1.53 mi W of Clay Works to 2.3 mi SSW of Ft Dodge
Cause: Heavy Rain
Property damage: $250,000
Reported by: Law Enforcement
Coordinates: 42.480, -94.210

Highway 169 was closed and impassable at the intersection of U.S. 20 Business in southern Fort Dodge.

Heavy Rain, Webster

When: August 10, 7:15 PM CST
Where: Webster County, 1.53 mi W of Clay Works
Reported by: Trained Spotter
Coordinates: 42.480, -94.210

Road closure at Highway 169, 4 miles north of Highway 20. Estimated 2 to 3 feet of standing water on underpasses with several cars stalled.

Hail, Calhoun

When: August 10, 7:26 PM CST
Where: Calhoun County, 1.68 mi WNW of Yetter
Measured: 1.25 in hail
Property damage: $5,000
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 42.330, -94.860

Trained spotter reported half dollar to possibly golf gall size hail.

Flash Flood, Webster

When: August 10, 7:30 PM CST to August 11, 12:00 AM CST
Where: Webster County, 0.84 mi NNW of Moorland to 0.66 mi N of Moorland Nesler Arpt
Cause: Heavy Rain
Property damage: $50,000
Reported by: Law Enforcement
Coordinates: 42.442, -94.304

Old Highway 20 underpass closed and impassable due to high water.

Flash Flood, Webster

When: August 10, 7:30 PM CST to August 11, 12:00 AM CST
Where: Webster County, 2.13 mi NNE of Burnside to 0.7 mi SSE of Kalo
Cause: Heavy Rain
Property damage: $100,000
Reported by: Law Enforcement
Coordinates: 42.380, -94.090

Washout in Dolliver State Park.

Heavy Rain, Polk

When: August 10, 8:07 PM CST to August 11, 2:07 AM CST
Where: Polk County, Polk City
Reported by: Mesonet
Coordinates: 41.770, -93.720

Measured rainfall was 4.94 inches at an automated gage near Big Creek in the last 6 hours.

Flash Flood, Hamilton

When: August 10, 8:07 PM CST to August 11, 12:00 AM CST
Where: Hamilton County, 0.86 mi NE of Stanhope
Cause: Heavy Rain
Property damage: $100,000
Reported by: Law Enforcement
Coordinates: 42.290, -93.790

Hamilton County Law Enforcement reports Highway 17 closed in Stanhope with water 3 feet deep over roads and storm sewers backing up into homes.

Heavy Rain, Boone

When: August 10, 8:13 PM CST to August 11, 2:13 AM CST
Where: Boone County, 3.78 mi SSW of Mackey
Reported by: Emergency Manager
Coordinates: 42.120, -93.800

Six inches of storm total rainfall since 1900 CST Tuesday night. Reported 3 miles south of Highway E18 on Highway 17.

Flash Flood, Webster

When: August 10, 8:15 PM CST to August 11, 12:00 AM CST
Where: Webster County, 1.23 mi NE of Lundgren to 0.65 mi NW of Burnside
Cause: Heavy Rain
Property damage: $50,000
Reported by: Trained Spotter
Coordinates: 42.360, -94.150

Water rushing over gravel road. Small creek by house was over its banks and observer said he hadn't seen runoff like this before.

Flash Flood, Webster

When: August 10, 8:20 PM CST to August 11, 12:00 AM CST
Where: Webster County, 2.81 mi N of Burnside to 1.6 mi ESE of Otho
Cause: Heavy Rain
Property damage: $100,000
Reported by: Trained Spotter
Coordinates: 42.390, -94.110

Water flowing over gravel roads with 3.9 inches of rainfall measured at 1930 CST. Additional rain from 2000 to 2020 CST.

Flash Flood, Bremer

When: August 10, 8:23 PM CST to August 11, 2:30 AM CST
Where: Bremer County, Waverly to 0.14 mi E of Waverly
Cause: Heavy Rain
Property damage: $50,000
Reported by: Law Enforcement
Coordinates: 42.730, -92.480

Water up to the top of tires on vehicles located at the intersection of 3rd Ave and 4th Street in northwest Waverly.

Heavy Rain, Calhoun

When: August 10, 8:30 PM CST
Where: Calhoun County, Pomeroy
Reported by: Trained Spotter
Coordinates: 42.550, -94.680

Highway 7 closed at underpass in Pomeroy due to flooding.

Thunderstorm Wind, Black Hawk

When: August 10, 8:45 PM CST
Where: Black Hawk County, 0.86 mi SW of Waterloo Ranch Arpt
Measured: 50 kt (58 mph) estimated gust
Property damage: $15,000
Reported by: Broadcast Media
Coordinates: 42.490, -92.290

Tree fell through a roof of a house along Fulton Street.

Flash Flood, Calhoun

When: August 10, 8:50 PM CST to August 11, 12:00 AM CST
Where: Calhoun County, 0.86 mi NE of Lytton to 1.28 mi NE of Lytton
Cause: Heavy Rain
Property damage: $10,000
Reported by: Law Enforcement
Coordinates: 42.440, -94.860

County Road N28 under water at the intersection with 240th St.

Flash Flood, Calhoun

When: August 10, 8:50 PM CST to August 11, 12:00 AM CST
Where: Calhoun County, 1.47 mi SSW of Knierim to 2.37 mi S of Knierim
Cause: Heavy Rain
Property damage: $10,000
Reported by: Law Enforcement
Coordinates: 42.430, -94.460

County Road P19 is under water 2 miles north of Highway 20.

Heavy Rain, Story

When: August 10, 8:52 PM CST to August 11, 2:52 AM CST
Where: Story County, 0.86 mi SW of Ontario
Reported by: Trained Spotter
Coordinates: 42.020, -93.690

Rainfall since 2100 CST was 3.86 inches.

Thunderstorm Wind, Tama

When: August 10, 8:53 PM CST
Where: Tama County, 0.86 mi SE of Montour
Measured: 50 kt (58 mph) estimated gust
Property damage: $2,000
Reported by: Law Enforcement
Coordinates: 41.960, -92.710

Large tree down on County Highway T47.

Flash Flood, Greene

When: August 10, 8:54 PM CST to August 11, 2:00 AM CST
Where: Greene County, 1.02 mi E of Hope to 1.67 mi ESE of Hope
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 42.200, -94.180

Water over County Highway P46 just south of the Webster County line.

Flash Flood, Boone

When: August 10, 8:57 PM CST to August 11, 2:00 AM CST
Where: Boone County, 1.54 mi W of Mackey to 1.6 mi E of Mackey
Cause: Heavy Rain
Property damage: $10,000
Reported by: Law Enforcement
Coordinates: 42.170, -93.800

Roads closed include 130th Street from Highway 17 to the county line. Water rushing over the road 4 to 5 inches deep and 50 feet wide.

Heavy Rain, Polk

When: August 10, 9:00 PM CST to August 11, 12:30 AM CST
Where: Polk County, 2.07 mi SW of Enterprise
Reported by: Trained Spotter
Coordinates: 41.710, -93.560

Rainfall since 2100 CST was 3.83 inches.

Flash Flood, Story

When: August 10, 9:05 PM CST to August 11, 2:00 AM CST
Where: Story County, 0.86 mi NE of Story City to 0.66 mi NE of Story City
Cause: Heavy Rain
Property damage: $25,000
Reported by: Emergency Manager
Coordinates: 42.190, -93.590

Broad Street was closed at Forest Ave in Story City due to water running over the road.

Heavy Rain, Hamilton

When: August 10, 9:23 PM CST
Where: Hamilton County, 5.67 mi E of Randall
Reported by: Trained Spotter
Coordinates: 42.220, -93.490

Rainfall of 3.5 inches and still raining with ditches full. Shallow water pooling around machine shed.

Flash Flood, Story

When: August 10, 9:29 PM CST to August 11, 2:00 AM CST
Where: Story County, 1.14 mi N of Story City to 0.58 mi NE of Story City
Cause: Heavy Rain
Property damage: $500,000
Reported by: Law Enforcement
Coordinates: 42.197, -93.601

Story City police reported widespread flooding throughout Story City. Had multiple reports of basement flooding with water backing up into them.

Flash Flood, Hamilton

When: August 10, 9:30 PM CST to August 11, 12:00 AM CST
Where: Hamilton County, 3.07 mi E of Stratford to 2.19 mi E of Stratford
Cause: Heavy Rain
Property damage: $10,000
Reported by: Law Enforcement
Coordinates: 42.270, -93.870

Highway 175 at the intersection of Fenton Ave is closed due to high water.

Flash Flood, Hamilton

When: August 10, 9:30 PM CST to August 11, 12:00 AM CST
Where: Hamilton County, 0.96 mi N of Jewell to 1.27 mi W of Randall
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 42.314, -93.651

Intersection of Highway 69 and County Highway D65/380th Street near Jewell has deep water over the road.

Flash Flood, Webster

When: August 10, 9:30 PM CST to August 11, 12:00 AM CST
Where: Webster County, 6.14 mi E of Dayton to 5.92 mi E of Dayton
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 42.270, -93.950

Highway 175 west of Stratford has 2 to 3 feet of water running over the road.

Flash Flood, Story

When: August 10, 9:48 PM CST to August 11, 2:00 AM CST
Where: Story County, 4.18 mi S of Zearing to 1.75 mi S of Zearing
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 42.110, -93.310

Water running over Highway 65 just south of Zearing.

Thunderstorm Wind, Polk

When: August 10, 10:00 PM CST
Where: Polk County, 1.55 mi W of Oralabor
Measured: 52 kt (60 mph) estimated gust
Property damage: $2,000
Reported by: Trained Spotter
Coordinates: 41.730, -93.660

A trained spotter estimated wind gusts of 60 MPH.

Flash Flood, Polk

When: August 10, 10:10 PM CST to August 11, 3:30 AM CST
Where: Polk County, 1.24 mi NE of Ankeny to 1.18 mi NE of Ankeny
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 41.740, -93.600

North Ankeny Boulevard and NE 9th Street was closed due to 16 to 18 inches of water in the intersection.

Heavy Rain, Hamilton

When: August 10, 10:22 PM CST
Where: Hamilton County, 1.68 mi ESE of Webster City Arpt
Reported by: Trained Spotter
Coordinates: 42.420, -93.840

Measured rainfall total of 3.75 inches.

Thunderstorm Wind, Cass

When: August 10, 10:29 PM CST
Where: Cass County, 0.52 mi W of Cumberland
Measured: 52 kt (60 mph) estimated gust
Reported by: Trained Spotter
Coordinates: 41.270, -94.890

Spotter estimated wind gust of 60 MPH.

Thunderstorm Wind, Cass

When: August 10, 10:40 PM CST
Where: Cass County, 0.52 mi W of Cumberland
Measured: 52 kt (60 mph) estimated gust
Property damage: $3,000
Reported by: Trained Spotter
Coordinates: 41.270, -94.890

Four inch tree branches blown down by thunderstorm winds.

Flash Flood, Polk

When: August 10, 11:16 PM CST to August 11, 3:30 AM CST
Where: Polk County, Ankeny to 0.28 mi N of Ankeny
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 41.730, -93.620

Deep impassable water at the intersection of west 1st Street and SW State Street in Ankeny.

Lightning, Story

When: August 10, 11:20 PM CST
Where: Story County, 0.42 mi N of Midvale
Property damage: $1,000
Reported by: Law Enforcement
Coordinates: 41.936, -93.569

Lightning struck a car on Interstate 35 at mile post 105. No injuries reported.

Flash Flood, Polk

When: August 10, 11:20 PM CST to August 11, 3:30 AM CST
Where: Polk County, 1.55 mi E of Ankeny to 1.54 mi E of Ankeny
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 41.730, -93.590

Up to 18 inches of running water across the intersectio nof SE 4th and Trilein in Ankeny.

Flash Flood, Polk

When: August 10, 11:31 PM CST to August 11, 3:30 AM CST
Where: Polk County, 1.99 mi W of Elkhart to 2.37 mi W of Farrar
Cause: Heavy Rain
Property damage: $50,000
Crop damage: $25,000
Reported by: NWS Employee
Coordinates: 41.785, -93.568

At least 6 inches of water running across Interstate 35 at mile post 97. Multiple cars spun out.

Thunderstorm Wind, Dallas

When: August 10, 11:53 PM CST
Where: Dallas County, 1.54 mi W of Woodward
Measured: 52 kt (60 mph) estimated gust
Property damage: $3,000
Reported by: Emergency Manager
Coordinates: 41.850, -93.960

The emergency manager estimated winds of 60 MPH.

Flash Flood, Polk

When: August 10, 11:54 PM CST to August 11, 3:30 AM CST
Where: Polk County, 2.18 mi ENE of Ankeny to 2.13 mi ENE of Ankeny
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 41.740, -93.580

Running water 2 feet deep on Delaware Ave in the 400 block.

Flash Flood, Grundy

When: August 10, 11:55 PM CST to August 11, 2:30 AM CST
Where: Grundy County, 6.15 mi NW of Fern to 7.09 mi WNW of Fern
Cause: Heavy Rain
Property damage: $25,000
Reported by: Law Enforcement
Coordinates: 42.530, -92.870

Water from an unknown creek overflowed onto 120th Street between H Ave and I Ave in northern Grundy County.

Flash Flood, Grundy

When: August 10, 11:55 PM CST to August 11, 2:30 AM CST
Where: Grundy County, 3.28 mi NW of Fern to 5.63 mi WNW of Stout
Cause: Heavy Rain
Property damage: $10,000
Reported by: Law Enforcement
Coordinates: 42.510, -92.820

Water of unknown depth running over 120th Street between I Ave and L Ave.

Flash Flood, Polk

When: August 11, 12:25 AM CST to 3:30 AM CST
Where: Polk County, 1.24 mi NE of Ankeny to 1.11 mi ENE of Ankeny
Cause: Heavy Rain
Property damage: $25,000
Reported by: Trained Spotter
Coordinates: 41.740, -93.600

Quick flowing water 4 to 5 inches in depth covering the intersection of Crestmoor Place and Northeast 6th Street.

Flash Flood, Marion

When: August 11, 12:35 AM CST to 4:30 AM CST
Where: Marion County, 0.52 mi E of Harvey to 0.16 mi SE of Harvey
Cause: Heavy Rain
Property damage: $50,000
Reported by: Emergency Manager
Coordinates: 41.320, -92.920

Six inches of water reported running through the streets of Harvey.

Flash Flood, Marion

When: August 11, 12:35 AM CST to 4:30 AM CST
Where: Marion County, 1.48 mi NNW of Tracy to 1.34 mi NNW of Tracy
Cause: Heavy Rain
Property damage: $10,000
Reported by: Emergency Manager
Coordinates: 41.300, -92.890

Water reported over 2 lanes of Highway T25 one quarter mile south of Highway 92.

Heavy Rain, Story

When: August 11, 12:37 AM CST
Where: Story County, 0.86 mi NE of Story City
Reported by: Mesonet
Coordinates: 42.190, -93.590

Rainfall of 4.20 inches was measured by an automated rain gage.

Flash Flood, Monroe

When: August 11, 3:26 AM CST to 6:14 AM CST
Where: Monroe County, 2.14 mi NNW of Georgetown to 1.98 mi ESE of Consol
Cause: Heavy Rain
Property damage: $10,000
Reported by: Law Enforcement
Coordinates: 41.050, -92.980

Water covering the road due to the Whippoorwill Creek at 170th Street.

Flash Flood, Polk

When: August 11, 3:55 AM CST to 6:00 AM CST
Where: Polk County, 0.59 mi SW of Santiago to 0.77 mi NNW of Santiago
Cause: Heavy Rain
Deaths: 1 direct, 0 indirect
Injuries: 4 direct, 0 indirect
Property damage: $100,000
Crop damage: $25,000
Reported by: Emergency Manager
Coordinates: 41.645, -93.439

Water rescue in progress regarding three vehicles with a total of 11 people near NE 8th Ave and NE 54th Ave. There was one fatality, 10 rescues and several injuries.

Lightning, Polk

When: August 11, 4:00 AM CST
Where: Polk County, 3.17 mi NNE of Ankeny
Property damage: $20,000
Reported by: Law Enforcement
Coordinates: 41.770, -93.590

House fire in north Ankeny caused by lightning.

Flash Flood, Polk

When: August 11, 4:40 AM CST to 7:00 AM CST
Where: Polk County, 0.86 mi NW of Santiago to 0.94 mi NE of Altoona
Cause: Heavy Rain
Property damage: $50,000
Crop damage: $25,000
Reported by: Emergency Manager
Coordinates: 41.660, -93.440

Flooding along Mud Creek.

Heavy Rain, Webster

When: August 11, 5:30 AM CST
Where: Webster County, 2.81 mi N of Burnside
Reported by: Trained Spotter
Coordinates: 42.390, -94.110

Overnight rainfall was 4.70 inches.

Flash Flood, Polk

When: August 11, 6:30 AM CST to 8:00 AM CST
Where: Polk County, 1.38 mi S of Des Moines to 1.29 mi N of Des Moines
Cause: Heavy Rain
Property damage: $100,000
Reported by: Fire Department/Rescue
Coordinates: 41.580, -93.620

Evacuations taking place from 3325 Hubble Ave at an apartment complex to 3560 Douglas Ave near a trailer Park in east Des Moines.

Heavy Rain, Polk

When: August 11, 8:17 AM CST
Where: Polk County, 0.52 mi E of Altoona
Reported by: Trained Spotter
Coordinates: 41.650, -93.460

A trained spotter measured 3.34 inches of rain overnight in Altoona.

Flood, Webster

When: August 11, 9:00 AM CST to August 12, 12:00 AM CST
Where: Webster County, 0.42 mi S of Gowrie to 1.37 mi N of Gowrie
Cause: Heavy Rain
Property damage: $200,000
Reported by: Trained Spotter
Coordinates: 42.274, -94.300

Several gravel roads closed by water in the Gowrie area that did not have a history of flooding. Overnight rainfall was 1.7 inches, with 7.7 inches in past 3 days.

Flood, Hamilton

When: August 11, 11:02 AM CST to August 12, 12:00 AM CST
Where: Hamilton County, 1.82 mi ESE of Stanhope to 2.54 mi WNW of Rosedale
Cause: Heavy Rain
Property damage: $200,000
Crop damage: $50,000
Reported by: Law Enforcement
Coordinates: 42.275, -93.765

Highway 17 was still closed due to flooding. County Highway R27 also closed south of Highway 175. Numerous gravel roads under several feet of water.

Flood, Story

When: August 11, 11:07 AM CST to August 12, 1:30 AM CST
Where: Story County, 0.86 mi SW of Ames to 1.89 mi NW of Ames
Cause: Heavy Rain
Property damage: $50 million
Reported by: Emergency Manager
Coordinates: 42.020, -93.630

Hilton Coliseum reported 4 to 6 feet of water inside flooding the stadium and basketball floor. Cy Stephens Auditorium also reports water in the mechanical building up to the 1st floor.

The people who died

As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.

Event	Date	Age	Sex	Where	Kind
Flash Flood, Polk	2010-08-11	16	Female	Vehicle/Towed Trailer	Direct

What these are

Funnel Cloud: A rotating column of cloud extending from a thunderstorm that did not reach the ground.
Heavy Rain: Rainfall totals unusual for the place and season that did not produce a flood.
Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Tornado: A violently rotating column of air in contact with the ground and extending from a thunderstorm, filed with its path, width and Fujita or Enhanced Fujita rating from the damage survey.
Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.
Lightning: A lightning strike that killed, injured or caused damage.
Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Iowa in 2010 Every state in 2010 This day in weather history The tornado archive for Iowa, 2010 Warnings in Iowa, August 2010

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 240011, 240016, 240036, 242387, 240038, 240013, 240017, 240012, 240014, 240043, 240080, 240015, 240010, 240081, 240082, 240030, 240073, 240032, 240078, 240079, 240087, 240039, 240019, 240084, 240085, 240033, 240018, 240088, 240086, 240034, 240061, 240020, 240062, 240074, 240075, 240083, 240063, 240021, 240053, 240022, and more.