A supercell thunderstorm produced large hail and wind damage in the northwest suburbs of the Chicago area during the afternoon hours of July 21st.  Additional thunderstorms developed during the evening hours of July 21st and continued into the early morning of July 22nd.

Thunderstorm Wind in WINNEBAGO, ILLINOIS
From 21-JUL-17 13:53:00 to 21-JUL-17 13:58:00 (CST-6)
Location: ROCKFORD
Magnitude: 60.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Numerous trees and power lines were blown down throughout Rockford.

Thunderstorm Wind in IROQUOIS, ILLINOIS
From 21-JUL-17 23:15:00 to 21-JUL-17 23:15:00 (CST-6)
Location: MARTINTON
Magnitude: 65.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Two houses on the southwest corner of Martinton near Route 1 had roof damage including one house with part of the roof blown off.  Utility poles were also blown down.

Hail in KANE, ILLINOIS
From 21-JUL-17 15:17:00 to 21-JUL-17 15:17:00 (CST-6)
Location: SLEEPY HOLLOW
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Hail in KANE, ILLINOIS
From 21-JUL-17 15:25:00 to 21-JUL-17 15:26:00 (CST-6)
Location: PINGREE GROVE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flood in OGLE, ILLINOIS
From 21-JUL-17 20:45:00 to 21-JUL-17 22:30:00 (CST-6)
Location: ROCHELLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

The intersection of Route 251 and 10th Avenue was flooded along with portions of 7th Street.

Flood in OGLE, ILLINOIS
From 21-JUL-17 20:45:00 to 21-JUL-17 22:30:00 (CST-6)
Location: FLAGG CENTER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Standing water was reported on roads in Flagg Center.

Flood in LA SALLE, ILLINOIS
From 21-JUL-17 22:37:00 to 22-JUL-17 00:00:00 (CST-6)
Location: OTTAWA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Up to five inches of standing water was reported covering Route 6 west of the Fox River.

Thunderstorm Wind in WILL, ILLINOIS
From 22-JUL-17 00:20:00 to 22-JUL-17 00:22:00 (CST-6)
Location: CREST HILL
Magnitude: 55.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Several large trees limbs were blown down along with a few trees uprooted in a several square block area north of Essington and Theodore Roads.

Thunderstorm Wind in KANE, ILLINOIS
From 21-JUL-17 15:25:00 to 21-JUL-17 15:25:00 (CST-6)
Location: PINGREE GROVE
Magnitude: 61.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Wind gusts were estimated to 70 mph.  Trees and power lines were blown down.

Thunderstorm Wind in DU PAGE, ILLINOIS
From 21-JUL-17 15:51:00 to 21-JUL-17 15:51:00 (CST-6)
Location: BLOOMINGDALE
Magnitude: 55.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A large tree was blown down.

Thunderstorm Wind in KANE, ILLINOIS
From 21-JUL-17 15:25:00 to 21-JUL-17 15:27:00 (CST-6)
Location: ELGIN
Magnitude: 70.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Wind gusts were estimated between 70 mph and 80 mph.  Hundreds of trees suffered damaged on the east side of Elgin.  Some trees were uprooted with large branches on cars.  Several roads were closed due to downed power lines.

Hail in COOK, ILLINOIS
From 21-JUL-17 15:49:00 to 21-JUL-17 15:51:00 (CST-6)
Location: SCHAUMBURG
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in COOK, ILLINOIS
From 21-JUL-17 15:50:00 to 21-JUL-17 15:53:00 (CST-6)
Location: ELK GROVE VLG
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DU PAGE, ILLINOIS
From 21-JUL-17 15:58:00 to 21-JUL-17 15:59:00 (CST-6)
Location: WOOD DALE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in DU PAGE, ILLINOIS
From 21-JUL-17 15:58:00 to 21-JUL-17 15:58:00 (CST-6)
Location: ITASCA
Magnitude: 64.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A wind gust to 74 mph was measured by a home weather station.

Hail in DU PAGE, ILLINOIS
From 21-JUL-17 15:55:00 to 21-JUL-17 15:56:00 (CST-6)
Location: ITASCA
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in DU PAGE, ILLINOIS
From 21-JUL-17 15:55:00 to 21-JUL-17 15:57:00 (CST-6)
Location: ITASCA
Magnitude: 78.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Many trees were blown down with some snapped at their base.  Based on radar and damage photos, it appears a microburst occurred with wind speeds estimated between 70 mph and 90 mph.

Thunderstorm Wind in COOK, ILLINOIS
From 21-JUL-17 15:55:00 to 21-JUL-17 15:57:00 (CST-6)
Location: ELK GROVE VLG
Magnitude: 78.00 EG
Property damage: 1.00M
Crop damage: 0.00K
Reported by: Public

Many trees were blown down with some snapped at their base. Based on radar and damage photos, it appears a microburst occurred with wind speeds estimated between 70 mph and 90 mph.  A 48 multi unit building complex suffered significant wind damage.

Hail in COOK, ILLINOIS
From 21-JUL-17 16:00:00 to 21-JUL-17 16:01:00 (CST-6)
Location: ELK GROVE VLG
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flood in COOK, ILLINOIS
From 21-JUL-17 15:50:00 to 21-JUL-17 17:30:00 (CST-6)
Location: SCHAUMBURG
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Water was reported on multiple roads in Schaumburg.

Flood in KANE, ILLINOIS
From 21-JUL-17 15:30:00 to 21-JUL-17 17:00:00 (CST-6)
Location: ELGIN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Water was reported on multiple roads in Elgin.  Rainfall of 1.33 inches was measured in 25 minutes.

Flash Flood in WINNEBAGO, ILLINOIS
From 21-JUL-17 14:00:00 to 21-JUL-17 16:00:00 (CST-6)
Location: ROCKFORD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Multiple streets were impassible due to flooding from heavy rain.

Funnel Cloud in IROQUOIS, ILLINOIS
From 21-JUL-17 19:16:00 to 21-JUL-17 19:17:00 (CST-6)
Location: CLIFTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A brief funnel cloud was reported near mile marker 297 on Interstate 57.

Funnel Cloud in IROQUOIS, ILLINOIS
From 21-JUL-17 19:38:00 to 21-JUL-17 19:39:00 (CST-6)
Location: DANFORTH
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter