Flash Flood in Illinois, August 2, 2001

Name: Flash Flood in Illinois, August 2, 2001
Start: 2001-08-02T06:30
End: 2001-08-02T11:00
Location: Illinois

August 2, 2001 · NWS LOT · 1 event in 1 county or zone

Thunderstorms developed over northern Cook county between 6 and 7 am on the morning of Thursday August 2nd. The storms slowly moved southeast across central and eastern Cook county.

Where it happened

Every event with a place to put it; 1 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

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The toll

Deaths: 0
Injuries: 0
Property damage: $37 million
Crop damage: None recorded
Events: 1

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.

Thunderstorms developed over northern Cook county between 6 and 7 am on the morning of Thursday August 2nd. The storms slowly moved southeast across central and eastern Cook county. The thunderstorms began to move out of southern Cook county between 10 and 11 am. Rain was falling at the rate of 3 to 4 inches per hour at some locations.Areas that had significant flooding include the Edens expressway at Pratt, where 6 to 8 feet of water covered the interstate and 3 cars were submerged. The Edens was closed from Touhy to Peterson. The Dan Ryan was closed and flooded between 83rd and 87th. Hubbard's cave was flooded and impassible. The underground parking garage at The Museum of Science and Industry was flooded and closed. Eisenhower at Kennedy had 3 to 4 feet of water covering the interstates. The Metra station at Van Buren was closed for a few hours due to flooding in one of the tunnels. Lakeshore Drive at Foster was flooded. Several people had to be rescued from their vehicles. 228 vehicles were reported to have been towed from flooded roads or viaducts. Many other smaller intersections and viaducts across the city of Chicago and parts of Cook county were flooded and impassible. No injuries were reported from the flooding.The Illinois Emergency Management Agency indicated that nearly 10,000 homes suffered some type of water damage during this event. Some rainfall totals include: 3.50 inches in Chicago between 730 am and 830 am, 3.58 inches at Burbank between 8 am and 11 am. Storm total rainfall was 4.78 inches at Chicago's Loop, 3.95 inches at Skokie, 3.95 inches at Wilmette, 3.50 inches at Wrigleyville, 3.41 inches at Willow Springs, 3.04 inches at Burr Ridge, 2.32 inches at Park Forest and 1.89 inches at Olympia fields. A 93 mile tunnel used to hold rain water during periods of heavy rain filled in just over an hour, holding approximately 1.6 billion gallons of water. The Chicago Park District opened locks at Wilmette and downtown Chicago to allow rain water to flow directly into Lake Michigan.In addition to the flooding, numerous reports of power lines and tree limbs blown down were received all across Cook county. Estimated wind speeds were between 40 and 50 mph. 56,000 customers lost power at the height of the storms.

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 Aug 2, 3:05 AM CST, 3 hours 25 minutes earlier.

Area forecast discussion, Aug 2, 3:05 AM CST, 3 hours 25 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
330 AM CDT THU AUG 2 2001

THUNDERSTORMS THAT DROPPED SOUTHEAST OUT OF SOUTHERN WI LAST EVENING
DIDN'T GET TOO FAR INTO NORTHERN IL BEFORE WEAKENING. EVEN THE
LINGERING SHOWERS IN NORTHEAST AND EAST CENTRAL IL HAVE ALL BUT
DISSIPATED. FRONTAL BOUNDARY EARLY THIS MORNING EXTENDING FROM
EASTERN LAKE SUPERIOR SOUTHWESTWARD ACROSS WI AND IA TO SOUTH
CENTRAL NEB WITH 3 DISTINCT AREAS OF ACTIVE CONVECTION...CENTRAL
HIGH PLAINS...NORTHERN IA AND SOUTHERN WI...WITH SOME FILLING IN
ALONG THE FRONT FROM WI TO IA. COMPARED TO CURRENT RADAR AND
SATELLITE IT APPEARS THAT THE AVN MODEL HAS THE BEST HANDLE ON THE
SITUATION PER ITS QPF...OMEGA AND ISENTROPIC FIELDS. FOLLOWING AVN
BRINGS UVV AND QPF MAX SOUTH-SOUTHEAST OUT OF SOUTHERN WI...ACROSS
NORTHEAST IL AND TO EAST CENTRAL IL AND NORTHWEST IND BY EVENING AS
SHORT WAVE ROTATES AROUND UPPER RIDGE ON SOUTHERN PERIPHERY OF
WESTERLIES. SOME HEAVIER RAINS POSSIBLE WITH SLOW MOVING CELL
MOVEMENT INDICATED ALONG WITH PRECIPITABLE WATER OF 2 TO 2 1/2
INCHES. FRONT TO ONLY MAKE SLOW PROGRESS AND AGAIN PREFER AVN HERE
WHICH IS SLOWEST IN PUSHING IT INTO NORTHWESTERN AND FAR
NORTHEASTERN IL THIS AFTERNOON...AND EVENTUALLY INTO CENTRAL IL
OVERNIGHT. CLOUDS AND LOCALLY COOLED AIR FROM TSRA SHOULD KEEP TEMPS
IN THE 85 TO 90 DEGREE RANGE. DEW POINTS STILL HIGH BUT HEAT INDEX
VALUES WILL BE BELOW HEADLINE THRESHOLD. WILL STILL KEEP MENTION OF
HUMID CONDITIONS IN FORECAST THOUGH. SLIGHTLY COOLER AND DRIER AIR
TO ARRIVE FRIDAY AS THE SURFACE RIDGE AND ITS LOWER 60S DEW POINTS
CURRENTLY OVER THE DAKOTAS MOVES EAST INTO THE WESTERN LAKES REGION.

.CHI...NONE.

TRS

In the hours before

Special weather statement, Aug 2, 5:18 AM CST, 1 hour 12 minutes before

ILZ003>006-008-010>014-019>023-032>033-039-INZ001>002-010>011-019-
021700-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
600 AM CDT/EST THU AUG 2 2001

FOR NORTH CENTRAL AND NORTHEAST ILLINOIS AND NORTHWEST INDIANA...

NO HAZARDOUS WEATHER IS EXPECTED TODAY OR TONIGHT.

THERE WILL BE SOME THUNDERSTORMS TODAY AHEAD OF A COLD FRONT AS IT
SLOWLY MOVES SOUTHEASTWARD INTO NORTHERN ILLINOIS...BUT THEY ARE NOT
EXPECTED TO BE SEVERE.  THE COLD FRONT WILL MOVE THROUGH NORTHERN
ILLINOIS AND NORTHWEST INDIANA TONIGHT...ENDING THE THREAT OF STORMS
THIS EVENING.  AS HIGH PRESSURE MOVES EAST INTO THE UPPER MIDWEST
FRIDAY...A LITTLE COOLER AND DRIER AIR WILL SPREAD INTO TmHE AREA.

TRS

The radar

The Chicago radar (KLOT), 49 km away, was scanning. The volume nearest the first event began at 12:29 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Cook

When: August 2, 6:30 AM CST to 11:00 AM CST
Where: Cook County, Countywide
Property damage: $37 million
Reported by: BROADCAST MEDIA
Coordinates: 41.895, -87.646 (the zone’s center; the record gives no point)

What these are

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.

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

The same day elsewhere

Every storm in Illinois in 2001 Every state in 2001 This day in weather history Warnings in Illinois, August 2001

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: 5264192.