Thunderstorms with extremely heavy rain developed along a stationary front and moved from northeast Iowa into northwest Illinois.  Some locations measured 5 to 7 inches of rainfall, causing localized flash flooding and pushing numerous creeks out of their banks.  Yellow Creek in Stephenson County was particularly hard-hit.
Pushing numerous rivers and creeks to bankfull or even out of their banks, this round of rainfall further set the stage for the extreme flooding that developed with the next round of storms later that night.

Flash Flood in CARROLL, ILLINOIS
From 23-JUL-10 03:00:00 to 23-JUL-10 17:00:00 (CST-6)
Location: MARCUS
Flood cause: Heavy Rain
Property damage: 1000.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Heavy rains of 3 to 9 inches fell across Carroll County during the late evening hours of July 22 and through the morning hours of July 23 resulting in flash flooding of much of the county.  Several roads across the county, especially the northern half, were closed due to the flash flooding.  The Shannon area received over 8 inches of rain during the night and was in need of sludge pumps to assist with the flooding issues in the area.  Areas that had never flooded before were flooded.

Flash Flood in JO DAVIESS, ILLINOIS
From 23-JUL-10 02:15:00 to 23-JUL-10 17:00:00 (CST-6)
Location: EAST DUBUQUE
Flood cause: Heavy Rain
Property damage: 1000.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rains of 3 to 9 inches fell across Jo Daviess County during the late evening of July 22 and through the morning of July 23 resulting in flash flooding of much of the county.  At 315 am CDT, water was over Highway 20 near Galena and Highway 35 near East Dubuque.  Apple River overflowed its banks due to the flash flooding.  In Elizabeth, water was flowing out of manhole covers.  In addition, Lone Street and Apple River Road were closed due to the flood waters.  At 940 am CDT, water rescues were in progress in Elizabeth.  Several roads were closed due to flooding.

Flash Flood in STEPHENSON, ILLINOIS
From 22-JUL-10 23:48:00 to 23-JUL-10 17:00:00 (CST-6)
Location: WADDAMS GROVE
Flood cause: Heavy Rain
Property damage: 1000.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Heavy rains of 2.5 to 6 inches fell across Stephenson County the evening hours of July 22 and through the morning of July 23 resulting in flash flooding of much of the county.  At 1248 am CDT, Freeport was flooded with about 10 inches of water in the streets.  Several roads were completely covered with water, especially in the vicinity of the Taylor Park District and near Route 75.  The flood waters came up to the middle of car tires.  Just before 130 am CDT, WREX TV relayed a report from a Freeport viewer that there was standing water everywhere.  At 405 am CDT, several homes in Pearl City were flooded. Some of the residences on the north side of town had flood waters up to the first floor level.  In addition, the city's sewer system was overwhelmed with the flood waters blowing some manhole covers off.  Route 73 near Pearl City was closed due to 8 inches of water flowing across the road, and Yellow Creek began flooding some nearby homes.  Highway 26 just south of Freeport was also closed due to flooding.  Trained spotters, CO-OP observers, the general public, WREX TV, and emergency management all contributed to this report.