69
Recorded events
0
Direct deaths
0
Direct injuries
$24.3M
Property damage
Flash Flood in Grant County, Wisconsin: 69 recorded events between 1997 and 2025. The strongest on record measured 0. That places the county #349 nationally and #1 statewide for this hazard.
Decade by decade
Flash Flood in Grant County, Wisconsin: events per decade
Reporting practice changed over time — early decades are undercounted, not calmer.
The busiest decade for flash flood in Grant County is the 2000s, when 29 of the county's 69 recorded events were logged. Comparing decades is useful for spotting active periods, but the earliest years are thin because systematic reporting for this hazard began later.
Within the Grant County archive, flash flood makes up 8.4% of all recorded severe weather across 8 hazard types. Nationally the county sits at #349 for this hazard and #1 within Wisconsin, putting it in the 88.6 percentile of all U.S. counties.
Seasonality
Events by month
Jul is the peak month for flash flood in Grant County with 24 recorded events, while Jan is the quietest. Seasonality here is a property of the archive as much as the climate: reports cluster where population and spotter networks are densest.
Most recent
Latest recorded events
| Date | Location | Magnitude | Damage |
|---|---|---|---|
| Aug 17, 2025 | LANCASTER | 0 | $75K |
| Aug 11, 2025 | LANCASTER | 0 | $5K |
| Aug 10, 2025 | BAGLEY | 0 | $300K |
| Aug 10, 2025 | BLUE RIVER | 0 | $25K |
| Jul 11, 2025 | FIVE PTS | 0 | $0 |
| Jul 11, 2025 | LANCASTER | 0 | $25K |
| Jul 11, 2025 | BIG PATCH | 0 | $10K |
| Jul 11, 2025 | DICKEYVILLE | 0 | $0 |
| Jul 11, 2025 | LOUISBURG | 0 | $5K |
| Jul 2, 2024 | BEETOWN | 0 | $15K |
Other hazards here
More from Grant County
- Thunderstorm Wind 331
- Hail 252
- Flood 65
- Tornado 55
From the record
What the reports say
Written by National Weather Service staff at the time of the event · public domain
Very heavy rain produced flash flooding across the northeast part of Grant County. |In Boscobel, numerous houses became surrounded by water with evacuations needed, most streets were flooded and cars were under water. 650 homes were impacted by the flood waters with two dozen families displaced. County Roads M and S near Boscobel were impassable due to high water and several other county roads between Blue River and Fennimore were covered with water and impassable. Portions of County Road C southwest of Woodman were under water. The flooding washed out sections of State Highway 133 outside of Woodman and Blue River. Debris was washed down Glass Hollow and Dry Hollow Creeks where it became lodged across railroad bridges in Bagley producing flooding in the town. The railroad tracks through Woodman were washed out. Flooding debris blocked some roads around Patch Grove. 54 canoeists had to be rescued from the Wisconsin River because of rising water.
A major flash flood hit Grant County during the afternoon of June 12th impacting the communities of Lancaster, Potosi, Tennyson, Ellenboro, and other rural areas. Numerous rescues were performed from people trapped in cars, especially in the Potosi area where terrain enhanced the runoff from repeat thunderstorms. Several homes on Hippie Hollow Road in Potosi Township were destroyed along with damage to as many as 600 homes elsewhere in the region. Many highways and county roads suffered flood damage including major bridge and road infrastructure.
Flash flood waters backed up in town as debris blocked area bridges. The water was three to four feet deep in places and propane gas containers began floating on the Mississippi River. Property damage in town was extensive.
Quick answers
Frequently asked
How many flash flood events are on record in Grant County, Wisconsin?
69 flash flood events are recorded in Grant County between 1997 and 2025, causing 0 direct deaths.
What is the strongest flash flood recorded in Grant County?
The strongest flash flood on record in Grant County measured 0.
Where does the flash flood data for Grant County come from?
All events come from the NOAA/NCEI Storm Events Database, the federal public-domain archive of severe weather reports. Dates are UTC, damage is as reported and not inflation-adjusted, and the most recent entries may still be revised.
Cite this page
“Flash Flood in Grant County, Wisconsin.” Severe Weather History. severeweatherhistory.com/county/wisconsin/grant-county/flash-flood/ · Data: NOAA/NCEI, FEMA, U.S. Census — public domain.