Mosquito season in Pierce County, WI: when it starts and ends
Mosquito months in Pierce County
In a normal year mosquito season in Pierce County, WI starts around May 3 and ends around October 5, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Pierce County, and when
- Start tipping out standing water weekly by April 19.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 5.
- 1 West Nile case since 2016 (last 2023): you should use repellent at dusk July, more so if over 60.
Pierce County against the rest of WI
Pierce County has the 51st longest season of 72 WI counties, at 155 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 42.3°F.
- Clark County: May 2 to October 5 (156 days, 1 WNV)
- Washburn County: May 2 to October 6 (156 days, 0 WNV)
- Oconto County: May 4 to October 6 (155 days, 2 WNV)
- Door County: May 9 to October 11 (155 days, 0 WNV)
West Nile in Pierce County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Pierce County (0 neuroinvasive) across 1 year. The worst was 2023 with 1; the latest was 2023.
Background: when mosquitoes go away for the winter; how the dates are worked out.