Scattered thunderstorms produced heavy rain during the morning of September 11th.  A narrow swath of torrential rain fell across portions of the north side of Chicago causing widespread flash flooding and at least 2,000 basements to flood.  Rainfall amounts of 2 to 4 inches were common across much of northern Illinois with a heavier swath of 4 to 6 inches over northwest Illinois and over northeast Illinois including central DuPage and central Cook Counties.

Flash Flood in COOK, ILLINOIS
From 11-SEP-22 09:10:00 to 11-SEP-22 11:15:00 (CST-6)
Location: MAYWOOD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Interstate 290 was closed due to flooding near Des Plaines Avenue.

Flash Flood in DU PAGE, ILLINOIS
From 11-SEP-22 07:30:00 to 11-SEP-22 11:15:00 (CST-6)
Location: WESTMONT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

The intersection of Burlington Avenue and Cass Avenue was flooded with 6 to 8 inches of flowing water just north of the train tracks.

Flood in KENDALL, ILLINOIS
From 11-SEP-22 06:15:00 to 11-SEP-22 11:00:00 (CST-6)
Location: OSWEGO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Street flooding was reported in Oswego.

Thunderstorm Wind in KENDALL, ILLINOIS
From 11-SEP-22 06:05:00 to 11-SEP-22 06:05:00 (CST-6)
Location: OSWEGO
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

A photo shared on social media showed a healthy 9 inch diameter tree limb snapped near Cheshire Court and Canton Drive.

Flood in LAKE, ILLINOIS
From 11-SEP-22 13:00:00 to 11-SEP-22 18:00:00 (CST-6)
Location: HIGHLAND LAKE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Street flooding was reported in Grayslake.  Rainfall of 4.70 inches was measured one mile north northeast of Mundelein.

Flood in COOK, ILLINOIS
From 11-SEP-22 13:29:00 to 11-SEP-22 16:30:00 (CST-6)
Location: DES PLAINES
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Street flooding was reported in Des Plaines.

Flood in DU PAGE, ILLINOIS
From 11-SEP-22 07:00:00 to 11-SEP-22 11:00:00 (CST-6)
Location: NAPERVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Street flooding was reported in Naperville.  Rainfall of 5.61 inches was measured six miles south southwest of Naperville with 2.6 inches falling in about one hour ending at 7:15 am CST.

Flood in DU PAGE, ILLINOIS
From 11-SEP-22 07:30:00 to 11-SEP-22 11:15:00 (CST-6)
Location: DOWNERS GROVE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Photos shared on social media showed portions of Hummer Park were flooded from the north branch of St. Joseph Creek.  The park was designed to flood in heavy rain events.  Rainfall of 4.78 inches was measured in Downers Grove with 2.87 inches falling in one hour ending at 7:45 am CST.

Flash Flood in COOK, ILLINOIS
From 11-SEP-22 08:09:00 to 11-SEP-22 11:15:00 (CST-6)
Location: MONT CLARE
Flood cause: Heavy Rain
Property damage: 3.10M
Crop damage: 0.00K
Reported by: Broadcast Media

A supercell thunderstorm moved across portions of central Cook County and the north side of Chicago producing a narrow swath of torrential rainfall with amounts of 4 to 6 inches.  Flash flooding developed across many areas with streets quickly becoming flooded which numerous stranded vehicles in the flood waters.  A car was stuck in flood waters in the 4800 block of Ravenswood Avenue where a woman and two children were rescued.  Significant flooding occurred along Foster, Lawrence and Bryn Mawr Avenues where cars were stalled in flood waters and some drivers needed to be rescued.  A car was stuck in a flooded viaduct at 1800 Foster Avenue.  A car was stuck in a flooded viaduct at Foster Avenue and Lake Shore Drive.  A car was stuck in flood waters in the 2700 block of Diversey Avenue.  A photo was shared on social media showing three cars stuck in flood waters near Irving Park Road and Kilbourne Avenue.  Numerous residential streets were flooded with 1 to 2 feet of standing water.  A nursing home was flooded along Western Avenue.  An estimated 2,000 basements suffered some amount of flooding.  Water was seen shooting up from various sewers which was likely due to pressure differences in the vast sewer system and the localized nature of the heaviest rain.
The highest rainfall totals included 5.90 inches in Lincoln Square where about 4 inches fell in 75 minutes ending at 8:55 am CST; 5.86 inches in Portage Park where about 3.4 inches fell in one hour ending at 8:30 am CST and 5.63 inches in Albany Park where about 3.5 inches fell in one hour ending at 8:40 am CST.
The City of Chicago reported 8 homes suffered major water damage resulting in $84,000 in damages; 309 homes suffered minor water damage resulting in $2,519,000 in damages and 52 businesses suffered minor water damage resulting in $503,000 in damages.  Damage amounts were unknown for the remaining affected homes as well as vehicles that were affected by flooding.