Flash Flood — Waukesha, Wisconsin

2025-08-09 to 2025-08-10 · near Menomonee Falls, Waukesha, Wisconsin

Event narrative

Widespread flash flooding of streets, creeks, rivers, and low lying neighborhoods and homes occurred especially in New Berlin, Brookfield, Butler, Menomonee Falls, Elm Grove, and Muskego. Some of the more notable creeks or rivers that flooded were the Fox and Menomonee Rivers and their tributaries. The Butler Ditch, Jewel Creek, Root River, and other unnamed creeks also flash flooded. For all of Waukesha County, 3 homes were classified as destroyed, 310 homes and businesses sustained major damage, 221 with minor damage and 119 with affected damage. These damages were from a variety of 1st floor flooding, basement flooding, and foundation collapse. Residential sewage backups, and raw sewage released into rivers by many municipalities were common. A small number of complete road washouts and swift water rescues occurred, in addition to dozens of people stranded in their vehicles in deep, still water in low lying areas. More specifically, a partial road washout occurred on Lily Road in Menomonee Falls due to the flash flooding of a tributary of the Menomonee River. The large collapse of a Y-shaped intersection at Campbell Dr. and Campbell Ct. in Menomonee Falls also occurred due to the flash flooding of Butler Ditch. A car was swept away at this intersection but the occupant escaped with minor injuries. 130 St. in New Berlin was partially washed out from the flash flooding of a tributary of the Root River. A swift water rescue occurred on Beres Rd. in New Berlin when a car was swept off the road by floodwaters. Dozens of people were evacuated or relocated from their flooded homes and neighborhoods. Very brief rise into moderate flood stage along the Menomonee River at Menomonee Falls between 1-1:15 AM local time August 10.

Wider weather episode

A historic flash flood and record rainfall occurred over portions of the Milwaukee Metropolitan Area and Southeast WI resulting in damages in the $100s Millions. Warm, moist, and unstable air rose along a stalled front to produce numerous thunderstorms and more than 10 inches of rain in many locations. Widespread flash flooding of streets, creeks, rivers, and low lying neighborhoods occurred. A homeless camp in Milwaukee underneath 1st Street Bridge adjacent to the surge of record flooding on the Kinnickinnic River was swept away. One or two deaths may be a result of this flash flooding with a couple others missing. Thousands of residential homes or businesses sustained major flood damage with dozens classified as destroyed due to 1st floor flooding, basement flooding or foundation collapse. Residential sewage backups, and raw sewage released into rivers and Lake MI by many municipalities was common. A small number of complete road washouts and swift water rescues occurred, in addition to dozens of people stranded in their vehicles in deep, still water in low lying areas. First responders had difficulty getting to their 911 calls including stranded motorists and flooded neighborhoods, due to the numerous flooded roads. Dozens of people were evacuated or relocated from their flooded homes and neighborhoods. Longer duration areal flooding and river flooding, which ranged from moderate flooding to record flooding, then continued for a couple more days. In addition to the flash flooding, a couple hikers were struck by lightning, via a ground current from a nearby strike on a tree, on the Ice Age Trail near Palmyra. They were initially rendered unconscious but did survive.

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Source: NOAA Storm Events Database, event_id 1281030. Narrative written by the NWS forecast office that issued the report.