Weekend Rainfall Accumulations in Southern Wisconsin
The past weekend of August 9-10, 2025, brought a 100-to-1000-year flood event to Milwaukee and southeastern Wisconsin, causing severe damage and displacement. The region has been experiencing a state of emergency ever since.
Record-Breaking Rainfall
Milwaukee Mitchell International Airport recorded an astounding 5.74 inches of rain in a single day, surpassing the city's average total for the entire month of August [2]. This overwhelming rainfall overwhelmed Milwaukee's combined sewer system, resulting in 5.14 billion gallons of untreated wastewater spilling into rivers and Lake Michigan over 78 hours [1][5].
Hardest Hit Areas
The suburbs of Wauwatosa were particularly affected, with widespread infrastructure damage estimated at $23 million in Milwaukee County alone [1]. Despite previous investments totaling $580 million in green infrastructure and flood management, the catastrophic rainfall and flooding displaced families, damaged homes, businesses, and community centers, and impaired key transportation routes [1][3].
Emergency Responses and Recovery
Emergency crews conducted numerous water rescues, and significant impacts included power outages, downed wires, and hazardous road conditions [3]. Multiple levels of government declared states of emergency to marshal resources for recovery. Milwaukee County Executive David Crowley declared a county-wide emergency on August 10, followed by Governor Tony Evers' state emergency declaration on August 11 [1][3]. Governor Evers emphasized the extensive damage and the length of time and resources needed for recovery and formally requested federal disaster aid from FEMA [1][3].
Atmospheric Conditions
The flooding was driven by a combination of atmospheric conditions including high humidity, inflow of moisture from the southwest, and a localized low-pressure center (Mesoscale Convective Vortex) that intensified downpours into the early August 10 morning [2]. This was the worst flash flooding in southeastern Wisconsin since 2008 [2].
Ongoing Concerns and Updates
Storms on Tuesday and beyond could exacerbate the flooding situation [4]. It is crucial to exercise caution when encountering high water during this weather event [4]. The current weather situation in southern Wisconsin is still conducive to flooding [4]. The risk of driving through high water remains, as it is difficult to assess the depth and hidden dangers [4].
For updates on the flood situation, you can refer to our website15 News and our website15 First Alert weather apps.
References
- Milwaukee County declares state of emergency due to flooding
- Milwaukee County flooding: 10 things to know
- Governor Evers declares state of emergency due to flooding in southeastern Wisconsin
- Flooding concerns continue as storms persist in southern Wisconsin
- Milwaukee's combined sewer system overflowed, spilling billions of gallons of untreated wastewater
The unprecedented rainfall on August 10, 2025, that caused the severe flooding in Milwaukee and southeastern Wisconsin was not only due to high humidity and southern inflow of moisture but also a localized low-pressure center (Mesoscale Convective Vortex) that intensified the downpours. Despite numerous emergency responses and recovery efforts, the weather-forecasting suggests that continued storms could further aggravate the flooding situation. To stay updated on the flood situation, residents are advised to regularly check the weather forecasting on our website15 News and our website15 First Alert weather apps.
