Mosquito season in Polk County, WI: when it starts and ends
Mosquito months in Polk County
In a normal year mosquito season in Polk County, WI starts around April 29 and ends around October 9, about 23 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Polk County, and when
- Start tipping out standing water weekly by April 15.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 9.
- No West Nile cases since 2016, so bites in Polk County are a nuisance; check window screens.
Polk County against the rest of WI
Polk County has the 31st longest season of 72 WI counties, at 163 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 43.9°F.
- Brown County: April 30 to October 12 (164 days, 7 WNV)
- Eau Claire County: April 28 to October 8 (163 days, 3 WNV)
- Waushara County: April 30 to October 10 (163 days, 0 WNV)
- Monroe County: April 29 to October 8 (162 days, 2 WNV)
West Nile in Polk County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Polk County (0 neuroinvasive) across 3 years. The worst was 2012 with 1; the latest was 2012.
More: how the dates are worked out · when mosquitoes go away for the winter.