Mosquito season in Clark County, WI: when it starts and ends
Mosquito months in Clark County
In a normal year mosquito season in Clark County, WI starts around May 2 and ends around October 5, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Clark 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 5.
- 1 West Nile case since 2016 (last 2025): you should use repellent at dusk July, more so if over 60.
Clark County against the rest of WI
Clark County has the 49th longest season of 72 WI counties, at 156 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 42.8°F.
- Marathon County: May 2 to October 6 (157 days, 3 WNV)
- Shawano County: May 2 to October 7 (157 days, 4 WNV)
- Washburn County: May 2 to October 6 (156 days, 0 WNV)
- Pierce County: May 3 to October 5 (155 days, 1 WNV)
West Nile in Clark County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Clark County (1 neuroinvasive) across 2 years. The worst was 2025 with 1; the latest was 2025.
See how the dates are worked out, and when the season starts across the US.