Mosquito season in Marathon County, WI: when it starts and ends
Mosquito months in Marathon County
In a normal year mosquito season in Marathon County, WI starts around May 2 and ends around October 6, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Marathon County, and when
- Start tipping out standing water weekly by April 18.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 6.
- 3 West Nile cases since 2016 (last 2023): you should use repellent at dusk July, more so if over 60.
Marathon County against the rest of WI
Marathon County has the 47th longest season of 72 WI counties, at 157 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 43.4°F.
- St. Croix County: May 2 to October 7 (158 days, 4 WNV)
- Barron County: May 2 to October 6 (157 days, 2 WNV)
- Shawano County: May 2 to October 7 (157 days, 4 WNV)
- Clark County: May 2 to October 5 (156 days, 1 WNV)
West Nile in Marathon County
From 1999 to 2025, CDC ArboNET counted 7 human West Nile cases in Marathon County (4 neuroinvasive) across 7 years. The worst was 2023 with 1; the latest was 2023.
More: how the dates are worked out · when mosquitoes go away for the winter.