Mosquito season in Columbia County, WI: when it starts and ends
Mosquito months in Columbia County
In a normal year mosquito season in Columbia County, WI starts around April 25 and ends around October 13, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Columbia County, and when
- Start tipping out standing water weekly by April 11.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 13.
- No West Nile cases since 2016, so bites in Columbia County are a nuisance; check window screens.
Columbia County against the rest of WI
Columbia County has the 14th longest season of 72 WI counties, at 171 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 46.4°F.
- Sauk County: April 24 to October 15 (173 days, 0 WNV)
- Racine County: April 30 to October 20 (173 days, 4 WNV)
- Lafayette County: April 25 to October 13 (171 days, 1 WNV)
- Fond du Lac County: April 27 to October 14 (171 days, 4 WNV)
West Nile in Columbia County
CDC ArboNET lists no human West Nile cases for Columbia County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 7 of those years.
More: how the dates are worked out · when mosquitoes go away for the winter.