The 5.79" of rain at Milwaukee was over 4 times the old record for the date, and it was the second highest daily precipitation of all time, second only to the 6.81" on August 6, 1986.
The 3.62" at Madison broke the old record for the date of 2.21" in 1885.
The National Weather Service reports:
A large area of moderate to heavy rain moved through southern Wisconsin Thursday morning, dumping 1.5 to 2 inches of rain across areas west of Madison, and .50 to 1.5 inches of rain east of Madison, including the Milwaukee metropolitan area. Milwaukee's Mitchell International Airport received 1.44 inches of rain during that morning round. Madison's Dane County Regional Airport received 1.47 inches. This helped set the stage for the major flooding that ensued later in the day.Green Bay, Wisconsin has already set a new July monthly rainfall record with 7.84". The normal rainfall amount through July 22 is 2.43".
During the afternoon, a persistent band of strong to severe thunderstorms developed and moved very slowly over south central and southeast Wisconsin through the evening hours. The individual storms were moving quite fast, about 40 to 50 mph, but the line containing these storms didn't, resulting in storms repeatedly training, or moving, over the same area. WIdespread 3 to 4 inch amounts were reported along and either side of the I-94 corridor, with locally higher amounts of 5 to 8 inches. Widespread reports of flooding and flash flooding associated with the heavy rain were received across southern Wisconsin, sending rivers and streams above flood level and water flowing over roads and stalling cars. Traffic was stopped on various stretches of the interstate system throughout downtown Milwaukee at the height of rush hour. Many motorists were stranded in their cars until the waters receded enough for traffic to move again.
Mitchell Field recorded 5.79 inches for the day...breaking a record for the date. The previous record was 1.26 set in 1948. This also is the second highest daily rainfall total on record for Milwaukee. The greatest one-day precipitation record was the 6.81 inches which fell on August 6, 1986.
Madison also set a record for precipitation for the date at 3.62 inches. This beat the previous mark of 2.21 inches set in 1885. The 3.62 inches ranks 13th for the most precipitation in one day. The record is the 4.96 inches which fell on August 8, 1906.
Rainfall amounts of 3.5" to over 4" were reported in northern Illinois. Through 1 pm today, Rockford Illinois received 4.27", smashing the 1973 record of 1.73", and additional rainfall is possible through the rest of the day.
Flooding also occurred across Iowa, where the 2.24" broke the old daily record of 1.55" set in 1924 at Waterloo.
Images (click to enlarge): Southern Wisconsin precipitation for the 2 days ending July 23, 2010 from National Weather Service; Milwaukee sinkhole from Christian Science Monitor