A low pressure system moved towards northern Illinois during the evening hours, causing thunderstorms to develop in the afternoon and evening hours across northern Illinois and northwest Indiana. A moist environment helped to produce heavy rainfall across portions of northern Illinois. A brief tornado occurred across the Frankfort-Monee area. As the storm moved over northwest Indiana hail and wind damage occurred.

Tornado in WILL, ILLINOIS
From 18-SEP-15 15:44:00 to 18-SEP-15 15:53:00 (CST-6)
Location: ANDRES
Tornado F-scale: EF1
Property damage: 70000
Crop damage: 0
Reported by: Emergency Manager

A spotter was located near Green Garden Rd and Harlem and spotted the tornado looking southwest. Damage to a roof and wood swing set was reported at one home. Four to five homes suffered minor roof damage. Six tall trees were snapped and other trees were blown down, including 20 trees at a country club.

Heavy Rain in COOK, ILLINOIS
From 18-SEP-15 16:01:00 to 18-SEP-15 16:25:00 (CST-6)
Location: (MDW)MIDWAY ARPT CHI
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

COOP observer reported 0.85 inches of rain in 24 minutes.

Flash Flood in COOK, ILLINOIS
From 18-SEP-15 16:56:00 to 18-SEP-15 16:56:00 (CST-6)
Location: BRAINERD
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Elderly woman rescued from stalled vehicle near 92nd and Hoyne Ave by Chicago Fire Department.

Heavy Rain in KANE, ILLINOIS
From 18-SEP-15 17:44:00 to 18-SEP-15 18:04:00 (CST-6)
Location: ELGIN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHs observer reported 1.01 inches of rain in 20 minutes.  Since midnight 1.80 inches of rain had fallen.

Flash Flood in LA SALLE, ILLINOIS
From 18-SEP-15 18:10:00 to 18-SEP-15 18:20:00 (CST-6)
Location: MENDOTA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A portion of Rt. 251 was closed due to flooding following the heavy rainfall. Two miles southeast of Mendota 2.10 inches of rain fell in the past 90 minutes.

Heavy Rain in LA SALLE, ILLINOIS
From 18-SEP-15 16:45:00 to 18-SEP-15 18:15:00 (CST-6)
Location: MENDOTA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHs observer reported 2.10 inches in the past 90 minutes.

Flash Flood in LAKE, ILLINOIS
From 18-SEP-15 18:24:00 to 18-SEP-15 18:54:00 (CST-6)
Location: KNOLLWOOD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Intersection of Rt. 41 and Rt. 176 flooded.

Hail in IROQUOIS, ILLINOIS
From 18-SEP-15 19:35:00 to 18-SEP-15 19:35:00 (CST-6)
Location: WELLINGTON
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Vermillion County EMA also reported 55 mph winds.

Thunderstorm Wind in WILL, ILLINOIS
From 18-SEP-15 22:59:00 to 18-SEP-15 23:04:00 (CST-6)
Location: NORMANTOWN
Magnitude: 43.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Couple of trees down, as well as large branches down.

Flash Flood in DU PAGE, ILLINOIS
From 18-SEP-15 23:00:00 to 18-SEP-15 23:15:00 (CST-6)
Location: NAPERVILLE
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Torrential downpours with several inches of flowing water at the intersection of Ogden Ave and Washington St. Viaduct just south of intersection near Metra line was also flooded.