Tornado and Flash Flooding in Illinois, July 27, 2003

Name: Tornado and Flash Flooding in Illinois, July 27, 2003
Start: 2003-07-27T11:00
End: 2003-07-27T15:00
Location: Illinois

July 27, 2003 · NWS LOT · 15 events in 9 counties and zones

Where it happened

Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. 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: 0
Injuries: 2
Property damage: $15 million
Crop damage: None recorded
Events: 15

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 LOT wrote it up.

A line of severe thunderstorms moved east across north central Illinois during the early afternoon hours of July 27th. Additional thunderstorms developed ahead of the first line across the southern portions of the Chicago Metro area producing very heavy rain and widespread flooding. As the first line of severe storms reached Lee county, numerous trees, tree limbs and power lines were blown down in Amboy in Lee county. Trees were blown down onto houses in West Brooklyn, also in Lee county. Winds as high as 65 mph blew down trees, large tree limbs and power lines across many locations in La Salle county. Trees were blown down in La Salle. Trees were uprooted near Lake Holiday in far northeast La Salle county. Large tree limbs were blown down in Mendota, Norway and one mile east of Serena. A grain bin was crushed and partially lifted off its base in Ottawa and a tree fell onto a car in Seatonville, both in LaSalle county. Wind damage was widespread across Kendall county as well. Trees, large tree limbs and power lines were blown down in Plano, Newark and Oswego as well as many rural parts of the county. Trees were blown down blocking Illinois Route 71 west of Oswego. Trees 20 inches in diameter were blown down southeast of Plano along Lynwood Drive. Southwest of Plano, a large tree limb fell onto a roof and broke a skylight. Winds gusted to 74 mph in Sandwich in De Kalb county, where numerous large trees were blown down or uprooted and a 20 inch diameter tree fell onto house. Several trees and tents were blown down at an Antique show in Sandwich in DeKlab county where one person suffered a broken arm and another was hit in the head by a falling tent pole. Canopies were also blown off of stores in Sandwich. A two and a half foot diameter tree was snapped at its base in Morris in Grundy county. A gust to 60 mph was reported in Naperville in Will county. A one foot diameter tree was snapped in half on Winthrop Street, east of Larkin and north of Black Roads in Joliet. Large tree limbs and power lines were blown down in Kankakee. A tree fell onto power lines in Sheldon in Iroquois county.In addition to the strong winds and wind damage, very heavy rain fell across much of Will and southern Cook counties. Most of the rain fell in a two hour period with 5.00 inches reported in Shorewood, 4.90 inches at the National Weather Service office in Romeoville, 4.10 inches in Midlothian, 4.00 inches in Joliet, 3.56 inches in Orland Park, 3.50 inches in Plainfield and South Holland, and 2.05 inches in Plano in Kendall county. Widespread street flooding was reported across all of north and central Will and southern Cook counties and many homes and businesses suffered water and flood damage. Retention ponds were flooded and backing up into yards and streets in Plainfield in Will county. Creeks were overflowing their banks in Midlothian in Cook county. Several roads had two to four feet of standing water and were impassible, some roads were partially washed away. Several cars were submerged at the intersection of Lagrange and Nebraska streets in Frankfort in Will county. A Will county sheriff's car was destroyed when it pulled into a flooded subdivision and sank. Several people had to be rescued from their cars after becoming trapped by flood waters in Frankfort, Lockport, Joliet, and Plainfield in Will county. A creek bridge was washed away in Lockport township. A man indirectly died from the flooding after walking into his flooded basement and being shocked because the water was in contact with electricity. An alley between Illinois and Main Streets in Lemont in Cook county was partially washed away by fast flowing water. 100 homes and 13 businesses were flooded in Lemont. Flood waters surrounded several buildings in Tinely Park. A 15 foot berm was washed away in unicorpated Palos Township which caused massive street and basement flooding in the Sandberg Glen subdivision. Street flooding was also reported in Plano in Kendall county.

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 Chicago, IL wrote its last area forecast discussion before the first event at Jul 27, 5:30 AM CST, 5 hours 30 minutes earlier.

Area forecast discussion, Jul 27, 5:30 AM CST, 5 hours 30 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
630 AM CDT SUN JUL 27 2003

AVIATION DISCUSSION FOR 12Z TAFS

AT 10Z FRONT FROM NR MTTW-DBQ-S DSM. FRONT SHOULD PASS THRU CHI
TERMINALS BETWEEN 17-19Z WITH COUPLE HOURS EARLIER AT RFD. SO FAR
NOTHING BUT SOME CLOUDS ALONG FRONT AS CAP STILL HOLDING. ALL MODLES
SHOW VERY RAPID DESTABILIZATION BY 18Z WITH CAP GONE. THE MAIN Q IS
WILL TS DEVELOP AS FRONT IS MOVING THRU CHI OR JUST TO S. LOOKS LIKE
MOST LIKELY JUST S OF THE AIRPORTS BUT A VERY CLOSE CALL. THE LAKE
BREEZE BEHIND THE FRONT MIIGHT BE THE ADDED PUSH TO GET THINGS GOING
AS EVEN AT 10Z SPC MESO DATA SHOWS CAPES AOA 2500 IN AREA AND PRECIP
H2O ABOVE 1.8 INCHES. SO THE ONLY Q IS THE TIME OF INITIATION WHICH
SHOULD BE IN THE 17-19Z TIME FRAME. ONCE FRONT GOES THRU WINDS TURN
IN OFF LAKE. STILL EXPECT VFR CONDS AS LAKE TOO WARM TO INFLUENCE
ANY LO CLOUDS. WITH ALL THIS IN MIND WILL CARRY A VCTS IN CHI TAFS
FOR 2 HOURS SINCE CAN NOT CARRY PROB GROUP 1ST 9 HOURS AND NOT
ENOUGH CONFIDENCE TO HAVE A TEMPO GROUP.

AF

WEAK SURFACE FRONT APPEARS TO BE FROM ABOUT THE STRAIGHTS OF MAC TO
JUST N OF DSM AT 06Z. NW SURFACE WINDS WEAK BEHIND FRONT AND
PRESSURE RISES MINIMAL...SO NOT A REAL STRONG PUSH BEHIND IT. BAND
OF MID CLOUDS IN IR SATELLITE LOOP IS ALL THATS GOING ON ATTM AS AMS
IS STILL QUITE CAPPED AND BEST DYNAMICS WELL NORTH ACROSS SOUTHERN
CANADA. MID 70S DEWPOINTS HAVE POOLED AHEAD AND ALONG FRONT ACROSS
IOWA AND SRN WIS. WITH LITTLE CLOUD COVER TEMPS SHOULD CLIMB QUICKLY
THIS MORNING INTO MID 80S...AND MAY TOP SATURDAYS MAXES. AMS WILL
BECOME FAIRLY UNSTABLE WITH CAPES 2000 TO 2500 BUT STILL QUITE WARM
ALOFT AND CONVERGENCE AND UPPER SUPPORT WILL BE WEAK. FRONT MAY SLIP
THROUGH RFD AND CHI QUIETLY THIS MORNING BUT THUNDERSTORMS SHOULD
ERUPT OVER SOUTHER PART OF FORECAST AREA...MAINLY S OF 1-80 IN THE
AFTERNOON AND CONTINUE THROUGH EVENING. LAKE BREEZE MAY ADD TO
CONVERGENCE W AND S OF CHICAGO. MAIN THREAT NOW APPEARS TO BE HEAVY
RAIN IN VERY MOIST ENVIRONMENT WITH WEAK SHEAR.

A LITTLE CONCERNED ABOUT POSSIBILITY OF INSTABILITY SHOWERS MONDAY
AFTERNOON AS AREA WILL STILL BE UNDER THE INFLUENCE OF ERN CANADA
UPPER LOW AND POCKET OF -10 TO -12 AIR AT H5 OVER THE AREA. GUIDANCE
TEMPS LOOK GOOD MONDAY WITH SOME LAKE COOLING.

DRY AND PLEASANT TUESDAY. SW FLOW DEVELOPING AHEAD OF APPROACHING
SYSTEM FROM THE NW SO MINIMLA LAKE COOLING IF ANY. THEN UPPER LOW
DROPS IN WED. NEW MRF CREEPS LOW SLOWLY ACROSS THE GREAT LAKES THU
AND FRI. BASED ON THIS WILL ADD DIURNAL CLOUDS AND CHANCE OF
AFTERNOON SHOWERS AND THUNDERSTORMS INTO FRI. WILL KEEP THE WEEKEND
DRY FOR NOW. TEMPS SHOULD ALSO BE COOL THU UNDER THE INFLUENCE OF
THE COOL POOL BUT MODIFYING BY THE WEEKEND.

.CHI...NONE.

ALLSOPP

Hazardous weather outlook, Jul 27, 7:20 AM CST, 3 hours 40 minutes before

ILZ003>006-008-010>014-019-020>023-032-033-039-INZ001-002-010-011-019
-281100-

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHICAGO IL
820 AM CDT SUN JUL 27 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND NORTHEAST
ILLINOIS...NORTHWEST INDIANA...AND THE ADJACENT WATERS OF LAKE
MICHIGAN.

.DAY ONE... TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
THIS EVENING ALONG AND SOUTH OF THE INTERSTATE 80 CORRIDOR.
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG A WEAK...SLOW
MOVING COLD FRONT BY THIS AFTERNOON AND CONTINUE THROUGH THIS
EVENING. THIS AREA OF DEVELOPMENT WILL BE MOST INTENSE ALONG AND
SOUTH OF INTERSTATE 80.

MORNING SUNSHINE WILL HEAT THE AIR WELL INTO THE 80S. THIS COMBINED
WITH DEWPOINTS IN THE LOWER TO MIDDLE 70S WILL DESTABILIZE THE
ATMOSPHERE. ALTHOUGH CONVERGENCE ALONG THE FRONT WILL NOT BE VERY
STRONG...THE LAKE BREEZE MAY ENHANCE CONVERGENCE WEST AND SOUTH OF
CHICAGO AND IN NORTHWEST INDIANA. SOME OF THE STORMS MAY PRODUCE
LARGE HAIL AND DAMAGING WINDS...ALONG WITH ALWAYS DANGEROUS
LIGHTNING...AND HEAVY RAIN WHICH WILL LIKELY BE ENOUGH TO CAUSE
LOCALIZED FLOODING.

.DAYS TWO THROUGH SEVEN... MONDAY THROUGH SATURDAY

THERE IS A CHANCE OF THUNDERSTORMS WEDNESDAY AFTERNOON THROUGH
FRIDAY AFTERNOON.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED THIS AFTERNOON AND EVENING.

&&

           NWS CHICAGO WEBPAGE

    HTTP://WWW.CRH.NOAA.GOV/LOT (LOWER CASE)
OR  HTTP://WEATHER.NOAA.GOV/CHICAGO (LOWER CASE)

RLB

The radar

The Quad Cities radar (KDVN), 104 km away, was scanning. The volume nearest the first event began at 17:00 UTC.

Open the radar archive at this moment

Event by event

11 thunderstorm wind, 3 flash flood, 1 tornado. Local standard time, as filed.

Thunderstorm Wind, Lee

When: July 27, 11:00 AM CST to 11:05 AM CST
Where: Lee County, Amboy
Measured: 57 kt (66 mph) estimated gust
Reported by: LAW ENFORCEMENT
Coordinates: 41.717, -89.333

Flash Flood, Cook

When: July 27, 11:00 AM CST to 2:45 PM CST
Where: Cook County, South Portion
Property damage: $1.0 million
Reported by: LAW ENFORCEMENT
Coordinates: 41.895, -87.646 (the zone’s center; the record gives no point)

Thunderstorm Wind, La Salle

When: July 27, 11:05 AM CST
Where: La Salle County, Peru
Measured: 51 kt (59 mph) measured gust
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 41.333, -89.133

The Peru AWOS measured a gust to 59 mph.

Thunderstorm Wind, La Salle

When: July 27, 11:05 AM CST to 11:42 AM CST
Where: La Salle County, Countywide
Measured: 57 kt (66 mph) estimated gust
Reported by: TRAINED SPOTTER
Coordinates: 41.283, -88.867

Thunderstorm Wind, Lee

When: July 27, 11:15 AM CST
Where: Lee County, West Brooklyn
Measured: 57 kt (66 mph) estimated gust
Reported by: TRAINED SPOTTER
Coordinates: 41.700, -89.150

Flash Flood, Will

When: July 27, 11:30 AM CST to 2:45 PM CST
Where: Will County, North Central Portion
Property damage: $14 million
Reported by: GENERAL PUBLIC
Coordinates: 41.445, -87.979 (the zone’s center; the record gives no point)

Thunderstorm Wind, Kendall

When: July 27, 11:35 AM CST to 12:15 PM CST
Where: Kendall County, Countywide
Measured: 57 kt (66 mph) estimated gust
Reported by: EMERGENCY MANAGER
Coordinates: 41.683, -88.367

Thunderstorm Wind, De Kalb

When: July 27, 11:44 AM CST to 11:54 AM CST
Where: De Kalb County, Sandwich
Measured: 64 kt (74 mph) measured gust
Injuries: 2 direct, 0 indirect
Reported by: EMERGENCY MANAGER
Coordinates: 41.650, -88.617

Thunderstorm Wind, Will

When: July 27, 11:55 AM CST
Where: Will County, Naperville
Measured: 52 kt (60 mph) estimated gust
Reported by: EMERGENCY MANAGER
Coordinates: 41.783, -88.150

Flash Flood, Kendall

When: July 27, 12:00 PM CST to 3:00 PM CST
Where: Kendall County, Plano
Reported by: EMERGENCY MANAGER
Coordinates: 41.591, -88.429 (the zone’s center; the record gives no point)

Thunderstorm Wind, Will

When: July 27, 12:10 PM CST
Where: Will County, Joliet
Measured: 57 kt (66 mph) estimated gust
Reported by: GENERAL PUBLIC
Coordinates: 41.533, -88.100

Thunderstorm Wind, Grundy

When: July 27, 12:12 PM CST
Where: Grundy County, Morris
Measured: 52 kt (60 mph) estimated gust
Reported by: EMERGENCY MANAGER
Coordinates: 41.367, -88.417

Tornado, Kendall

When: July 27, 12:26 PM CST to 12:28 PM CST
Where: Kendall County, Yorkville
Rating: F0
Path length: 1 mi
Path width: 100 yd
Reported by: NWS STORM SURVEY
Coordinates: 41.633, -88.450

A weak tornado touchdown near the Hideaway Lake Camp near Yorkville in Kendall county. The main line of thunderstorms had already moved east of the area when a small thunderstorm developed near Yorkville and quickly interacted with a lake breeze moving west through the same area. This interaction helped to form a circulation which spun up as a weak tornado. Numerous trees were damaged and some were blown down. Damage occurred to several trailers and campers from the falling trees and tree limbs. The tornado appeared to skip along the ground with the strongest winds staying aloft affecting mainly the trees. The tornado lasted about two minutes.

Thunderstorm Wind, Kankakee

When: July 27, 12:28 PM CST
Where: Kankakee County, Kankakee
Measured: 50 kt (58 mph) estimated gust
Reported by: LAW ENFORCEMENT
Coordinates: 41.117, -87.850

Thunderstorm Wind, Iroquois

When: July 27, 12:55 PM CST
Where: Iroquois County, Sheldon
Measured: 50 kt (58 mph) estimated gust
Reported by: LAW ENFORCEMENT
Coordinates: 40.767, -87.567

What these are

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.
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.
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.

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

The same day elsewhere

Every storm in Illinois in 2003 Every state in 2003 This day in weather history The tornado archive for Illinois, 2003 Warnings in Illinois, July 2003

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: 5373998, 5374010, 5373999, 5374000, 5374006, 5374011, 5374001, 5374004, 5374003, 5374012, 5374005, 5374002, 5374009, 5374007, 5374008.