Heavy rain caused flooding along the Little Sioux and Ocheyedan Rivers during the middle part of August. the flooding was mostly minor to moderate, but a record high stage was recorded on the Ocheyedan River at Spencer.
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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.
The episode as NWS FSD wrote it up.
Heavy rain caused flooding along the Little Sioux and Ocheyedan Rivers during the middle part of August. the flooding was mostly minor to moderate, but a record high stage was recorded on the Ocheyedan River at Spencer.
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 Sioux Falls, SD wrote its last area forecast discussion before the first event at Aug 8, 3:40 AM CST, 2 hours 20 minutes earlier.
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
440 AM CDT SUN AUG 8 2010
.DISCUSSION...
STILL TWO BIG ISSUES WITH THIS FCST...HEAT/HUMIDITY HEADLINES AND
POTENTIAL FOR VERY HEAVY RAIN. FOR TODAY WARM AIR ALOFT WILL MIX
DOWN THIS AFTN...BUT HIGHER CLOUDS APPROACHING FROM WEST MAY PUT
SOME DAMPER ON POTENTIAL. HOWEVER...HUMIDITY WILL CONTINUE TO BUILD
UP WITH POOLING AND EVAPOTRANSPIRATION...SO HEAT/HUMIDITY HEADLINES
KEPT INTACT. THE QUESTION IS HOW THIS HEAT WILL HOLD UP FOR MON AS
HEAVY RAIN MCS EXPCD TO CRASH EWD OVER CWA TNGT...ESP SOUTH OF
I90...WITH ESELY FLOW OF SOMEWHAT RAIN COOLED AIR PSBL FOR MON.
HOWEVER...HIGH DEWPOINTS SHOULD MAKE UP FOR THAT ON MON. MODELS ALL
SHOW TROPICAL CONNECTION MCS MOVG EWD OVER CWA TNGT WITH THE USUAL
BIASES...CANADIAN REGIONAL A LIT TOO FAR NORTH...U.S. MODELS A LIT
TOO FAR SOUTH...AND ECMWF IN BTWN AND PROBABLY CLOSER TO RIGHT AS
MCS SHOULD RIDE THE CAP A LIT FURTHER NORTH. A FEW SVR STORMS PSBL
THIS EVE WITH HIGHEST INSTABILITY...BUT MAIN THREAT WILL BE HEAVY
RAINS TNGT. WITH HIGH PWATS AND CONVERGENCE EXPCD...AN FFA SHOULD
DEFINITELY BE CONSIDERED BY LATER SHIFTS ESP FOR AREA ALG AND SOUTH
OF I90 WHERE THERE ARE SERIOUS WATER ISSUES. EXPCD MCS PULLS OFF TO
SE OF AREA MON MRNG. WMFNT BOUNDARY AND DECENT CHCS TSTMS MOVES BACK
NORTH OVER AREA MON NGT AND TUES WITH MORE HEAVY RAIN PSBL. WMFNT
FLWD BY BRISK SLY FLOW OF VERY WARM AND HUMID AIR FOR TUES AND THIS
DAY SHOULD EASILY REACH HEAT HEADLINE CRITERIA IN SRN CWA. REST OF
FCST AFTER TUES NGT LEFT FOR DAYSHIFT TO PONDER./ RYRHOLM
&&
.AVIATION...
SFC WNDS HAVE DECOUPLED AT MOST LOWER ELEVATIONS SITES...MOST
NOTABLY KSUX. HOWEVER...LLJ IS ALSO VEERING AND WKNG...WHICH WL
ALLOW LLWS TO DIMINISH DURING PREDAWN HOURS. PATCHY MVFR VSBYS WL
PERSIST THRU 13Z...ESPECIALLY WHERE GRADIENT IS WEAKER TO W AND N OF
KFSD. VFR CONDITIONS WILL GENERALLY BE THE RULE PRIOR TO LATE DAY
CONVECTIVE DEVELOPMENT. STRENGTH OF MID LVL WARMING SHUD PRECLUDE
MENTIONABLE ACTIVITY PRIOR TO 00Z FOR KFSD/KSUX...BUT WITH SHORTWAVE
APPROACH EARLY EVNG...THE BEST CHANCE OF CONVECTION WILL BE DURING
THE EVENING AND OVERNIGHT HOURS...MAINLY ALG AND S OF INTERSTATE 90.
WHILE ISOLD SVR STORMS ARE POSSIBLE...A GREATER THREAT WL BE VERY
HEAVY RAINFALL...WITH STRONGER STORMS LKLY HAVING IFR VSBYS AND MVFR
CIGS COMMON. /CHAPMAN
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...EXCESSIVE HEAT WARNING FROM 1 PM SUNDAY TO 7 PM CDT MONDAY FOR
IAZ012>014-020>022-031-032.
HEAT ADVISORY FROM 1 PM SUNDAY TO 7 PM CDT MONDAY FOR IAZ001>003.
MN...HEAT ADVISORY FROM 1 PM SUNDAY TO 7 PM CDT MONDAY FOR MNZ098.
NE...EXCESSIVE HEAT WARNING FROM 1 PM SUNDAY TO 7 PM CDT MONDAY FOR
NEZ013-014.
SD...EXCESSIVE HEAT WARNING FROM 1 PM SUNDAY TO 7 PM CDT MONDAY FOR
SDZ068>071.
HEAT ADVISORY FROM 1 PM SUNDAY TO 7 PM CDT MONDAY FOR SDZ038-050-
052>054-057>067.
&&HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SIOUX FALLS SD 549 AM CDT SUN AUG 08 2010 SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098- IAZ001>003-012>014-020>022-031-032-NEZ013-014-091200- AURORA-BEADLE-BON HOMME-BROOKINGS-BRULE-BUENA VISTA IA- CHARLES MIX-CHEROKEE IA-CLAY-CLAY IA-COTTONWOOD MN-DAKOTA NE- DAVISON-DICKINSON IA-DIXON NE-DOUGLAS-GREGORY-HANSON-HUTCHINSON- IDA IA-JACKSON MN-JERAULD-KINGSBURY-LAKE-LINCOLN-LINCOLN MN- LYON IA-LYON MN-MCCOOK-MINER-MINNEHAHA-MOODY-MURRAY MN-NOBLES MN- OBRIEN IA-OSCEOLA IA-PIPESTONE MN-PLYMOUTH IA-ROCK MN-SANBORN- SIOUX IA-TURNER-UNION-WOODBURY IA-YANKTON- 549 AM CDT SUN AUG 08 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA... SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS... SCATTERED THUNDERSTORMS SHOULD DEVELOP LATE THIS AFTERNOON WEST OF INTERSTATE 29 AND NORTH OF INTERSTATE 90...AND THEN MERGE INTO A LARGE AREA OF THUNDERSTORMS MAINLY FROM SOUTHEAST SOUTH DAKOTA TO NORTHWEST IOWA THIS EVENING. LOCALLY DAMAGING WINDS AND LARGE HAIL WILL BE POSSIBLE...BUT THE MAIN THREAT FROM THESE THUNDERSTORMS WILL BE VERY HEAVY RAIN WITH 1 TO 3 INCHES RAINFALL POSSIBLY CAUSING LOCAL FLASH FLOODING TONIGHT. FLOODING... RIVER FLOODING WILL CONTINUE ALONG THE JAMES RIVER FOR AN EXTENDED PERIOD. RIVER FLOODING IS ALSO OCCURRING OVER PARTS OF THE VERMILLION RIVER...AND THE LITTLE SIOUX RIVER NEAR LINN GROVE IOWA. WITH NO ADDITIONAL RAINFALL THESE RIVERS WILL DROP BELOW FLOOD STAGE OVER THE NEXT FEW DAYS. EXCESSIVE TEMPERATURES... IT WILL BE HOT AND HUMID THIS AFTERNOON FROM SOUTHEAST SOUTH DAKOTA TO NORTHWEST IOWA AND FAR NORTHEAST NEBRASKA. HIGHEST HEAT INDICES THIS AFTERNOON SHOULD BE FROM 105 TO 110 IN THE LOWER JAMES VALLEY OF SOUTH DAKOTA TO NORTHWEST IOWA...AND 95 TO 100 ELSEWHERE IN THE AREA. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY VERY WARM AND HUMID AIR WILL CONTINUE TO CAUSE UNCOMFORTABLE CONDITIONS MONDAY AFTERNOON THROUGH TUESDAY...ESPECIALLY SOUTH OF INTERSTATE 90. AFTERNOON HEAT INDICES WILL GENERALLY RANGE FROM AROUND 105 SOUTH TO 95 NORTH IN THE FORECAST AREA. IN ADDITION...SCATTERED THUNDERSTORMS WITH LOCALLY HEAVY RAINS WILL AGAIN BE POSSIBLE MONDAY NIGHT AND EARLY TUESDAY IN THE AREA...ESPECIALLY ALONG AND NORTH OF INTERSTATE 90. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL BE POSSIBLE AFTER 5 PM CDT. && FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK.
The national radar mosaic for the moment the first event began.
4 flood. Local standard time, as filed.
Heavy rain caused minor to moderate flooding along the Little Sioux River, with farmland and some other lowlands flooded. The river crested at 1.82 feet above flood stage at Linn Grove on August 14th.
Heavy rain caused record flooding along the Ocheyedan River, with farmland, other lowlands, and a few roads flooded. The river crested at a record 3.70 feet above flood stage near Spencer on August 11th.
Heavy rain caused moderate flooding along the Little Sioux River, with farmland, other lowlands, and a few roads flooded. The river crested at 4.28 feet above flood stage at Spencer on August 12th.
Heavy rain caused minor to moderate flooding along the Little Sioux River, with farmland and some other lowlands flooded. The river crested at 2.30 feet above flood stage at Cherokee on August 12th.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2010Every state in 2010This day in weather historyWarnings in Iowa, August 2010
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: 257595, 257591, 257587, 257597.