Flood — Ozaukee, Wisconsin

2025-08-10 to 2025-08-12 · near Bayside, Ozaukee, Wisconsin

Event narrative

The continued areal flooding of streets, creeks, rivers, and low lying neighborhoods in Mequon, Thiensville, Cedarburg and southern Grafton. More specifically, the flooding of Pigeon Creek washed out a portion of Highland Rd. The flooding of Olau Creek flooded Pioneer Rd. just west of Port Washington Rd., and also flooded Port Washington Rd. just north of Pioneer Rd. The same creek flooded a portion of Bonniwell Rd. The flooding of the Little Menomonee River flooded a portion of County Line Rd. between Tamerlane Dr. and Granville Rd. The Mequon Nature Preserve experienced flooding including its Education Center. Other roads were closed near the flooded Milwaukee River, which included many roads in a neighborhood near the River Forest Nature Preserve. Other roads flooded and closed due to the flooding of the Milwaukee River were a portion of Green Bay Rd. in Thiensville, River Rd. from Donges Bay Rd. to County Line Rd., and Island Dr. from East Shoreland Dr. to Circle Dr. Sections of I-43 were closed due to flooding. This included I-43 northbound from Pioneer Rd. to Hwy 60. Only one lane of I-43 southbound was open. The I-43 southbound exit ramps to Grafton and Mequon Rd. were closed. Moderate flooding of the Cedar Creek at Cedarburg occurs during the morning and afternoon hours of August 12, with a crest of 11.03 feet occurring at 10:15 AM local time August 12. Moderate river flooding of the Cedar Creek at Cedarburg leads to the closure of Cedar Creek Park in downtown Cedarburg, in addition to the inundation of backyards of some homes and businesses along Sheboygan Rd in the community of Cedarburg. Moderate river flooding continues until 3 PM local time August 12.

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 1283068. Narrative written by the NWS forecast office that issued the report.