An extreme rainfall event occurred on July 2 in the Chicago metropolitan area caused by multiple nearly stationary bands of showers and thunderstorms near a slow-moving low pressure area. Rainfall occurred over from approximately 12 AM CST to 6 PM CST, with peak rainfall rates exceeding 2 inches per hour and storm total accumulations nearing 9.0 inches in Cook County. Individual showers and thunderstorms moved very slowly during the event, with storm motions of 15 mph or less, leading to extended periods of heavy rainfall. The area of peak rainfall just west of Chicago was estimated to have less than a 1% chance of occurring annually, and led to widespread flooding of basements, streets, and expressways. Also happening on this day was the first annual NASCAR Chicago street race downtown. The storm temporarily flooded portions of the race course, caused a number of delays and cancellations of events, and made conditions terribly slick for the drivers on the course.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:30:00 (CST-6)
Location: (MDW) CHICAGO MIDWAY AIRPORT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCHICA656, recorded 6.34 inches of storm total rainfall.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:30:00 (CST-6)
Location: PILSEN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCHICA920, recorded 5.9 inches of storm total rainfall.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 14:04:00 (CST-6)
Location: WEST TOWN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCHICA498, recorded 6.85 inches of rainfall between roughly 6 AM and 2 PM CST.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:30:00 (CST-6)
Location: LAKEVIEW
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCHICA677, recorded 7.89 inches of storm total rainfall.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 14:04:00 (CST-6)
Location: LINCOLN PARK
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCHICA677 , recorded 7.23 inches of rainfall between roughly 6 AM and 2 PM CST.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 14:09:00 (CST-6)
Location: BERWYN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCICER16 , recorded 8.21 inches of rainfall between roughly 6 AM and 2 PM CST.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:30:00 (CST-6)
Location: LINCOLN PARK
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCHICA790, recorded 7.36 inches of storm total rainfall.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:00:00 (CST-6)
Location: CICERO
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A USGS rain gauge at Cicero recorded 8.6 inches of storm total rainfall.

Flash Flood in COOK, ILLINOIS
From 02-JUL-23 08:40:00 to 02-JUL-23 17:30:00 (CST-6)
Location: EVANSTON
Flood cause: Heavy Rain
Property damage: 500.00M
Crop damage: 0.00K
Reported by: Emergency Manager

Throughout much of central Cook County including Chicago and nearby suburbs, very heavy rainfall caused widespread flash flooding of roadways and structures. During a 12-hour period from 3 AM to 3 PM CST, storm total rainfall in Cook County ranged from 1-9 inches, with the highest amounts in central Cook County near the border of Chicago, Cicero, and Oak Park. The magnitude of this rainfall ranged from typical to extreme, with the peak rainfall estimated to have less than a 0.2% chance of occurring in a given year. Two distinct waves of heavy rainfall occurred in the Chicago area during this event, with each period of heavy rainfall corresponding to significant flooding.
The first wave of heavy rainfall impacted the Chicago area from 4:30 AM to 11 AM CST. Within a few hours numerous residential streets were flooded and I-290 (Eisenhower Expressway) was blocked in multiple locations, as well as a stretch of I-55 (Stevenson Expressway) near Pulaski Road. Multiple water rescues were reported, most of which occurred at underpasses in Chicago and the immediate western suburbs. Runoff quickly entered the deep tunnel system and mostly filled McCook Reservoir, greatly reducing storage capacity for additional rainfall.
After a brief period with lighter rainfall intensities from 11 AM to 12:30 PM CST, the second wave of heavy began, which occurred until 3:30 PM CST. This additional rainfall brought renewed flooding of numerous roadways as well as portions of CTA's blue and pink El train lines. The storage capacity of the deep tunnel and McCook Reservoir were exceeded, with most rainfall flowing into the Chicago River system as part of a combined sewer overflow event. The Chicago River quickly rose to minor flood stage, flooding the Chicago Riverwalk. MWRD opened gates at Chicago Lock to reverse the flow of the river into Lake Michigan, causing a mixture of rainfall and untreated sewage to enter the lake. The lack of capacity to store combined rain water and sewage caused rainfall to back up into 10s of thousands of basements. As of November 29th, 2023, FEMA had received nearly 75,000 claims for flooded homes, the majority of which are assumed to be basement flooding. Approximately $285 million in FEMA individual assistance grants were provided, along with $96.5 million in low-interest SBA loans. These federal disaster assistance programs only cover a portion of uninsured losses. Few claims, less than $1 million in total, were made to the National Flood Insurance program due to the low percentage of residents paying for such polices and the cause of most instances of flooding being related to sewer backup. The estimated total damage costs from this flash flood event are likely in excess of $500 million.

Flash Flood in COOK, ILLINOIS
From 02-JUL-23 08:23:00 to 02-JUL-23 12:00:00 (CST-6)
Location: ARCHER HEIGHTS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Interstate 55 near Pulaski Road was closed due to floodwater on the interstate.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:30:00 (CST-6)
Location: WEST TOWN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCHICA498, recorded 8.12 inches of storm total rainfall.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:30:00 (CST-6)
Location: BERWYN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILCICER16, recorded 8.96 inches of storm total rainfall.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:30:00 (CST-6)
Location: LA GRANGE PARK
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILBROOK16, recorded 4.99 inches of storm total rainfall.

Flash Flood in DU PAGE, ILLINOIS
From 02-JUL-23 08:30:00 to 02-JUL-23 12:00:00 (CST-6)
Location: DOWNERS GROVE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

An NWS employee reported as many as 6 inches of standing water on Main St in Downers Grove between 63rd St and 75th St.

Flash Flood in WILL, ILLINOIS
From 02-JUL-23 08:40:00 to 02-JUL-23 12:15:00 (CST-6)
Location: BOLINGBROOK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

An NWS employee reported more than 6 inches of standing water underneath the overpass at I-55 and Joliet Rd in Bolingbrook.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 00:00:00 to 02-JUL-23 11:42:00 (CST-6)
Location: STICKNEY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A member of the public recorded 5.27 inches of rain in Berwyn from the start of the day through roughly 11:30 AM CST.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 00:00:00 to 02-JUL-23 11:17:00 (CST-6)
Location: LA GRANGE PARK
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

A personal weather station picked up 4.35 inches of rain from the start of the day through roughly 11AM CST. The owner of the weather station confirmed the observation with a standard rain gauge.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 00:00:00 to 02-JUL-23 11:58:00 (CST-6)
Location: GOLD COAST
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The weather station at the Latin School of Chicago recorded 4.76 inches of rainfall from the start of the day through roughly 12:00 PM CST.

Heavy Rain in DU PAGE, ILLINOIS
From 02-JUL-23 08:25:00 to 02-JUL-23 08:55:00 (CST-6)
Location: WOODRIDGE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

An NWS employee recorded 1.7 inches of rain in a 30 minute period.

Heavy Rain in WILL, ILLINOIS
From 02-JUL-23 07:30:00 to 02-JUL-23 09:42:00 (CST-6)
Location: CRYSTAL LAWNS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A Cocorahs observer recorded 2.54 inches of rain between approximately 7:30 AM and 9:40 AM CST.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 09:53:00 (CST-6)
Location: (MDW) CHICAGO MIDWAY AIRPORT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

The ASOS at Chicago Midway Airport recorded 2.94 inches of rain between approximately 6 AM and 9:50 AM CST. Of those 2.94 inches, 1.6 fell within the latest hour.

Heavy Rain in COOK, ILLINOIS
From 02-JUL-23 06:00:00 to 02-JUL-23 17:30:00 (CST-6)
Location: FOREST VIEW
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A private weather station, KILSTICK6, recorded 7.47 inches of storm total rainfall.