Mosquito season in La Crosse County, WI: when it starts and ends
Mosquito months in La Crosse County
In a normal year mosquito season in La Crosse County, WI starts around April 20 and ends around October 17, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in La Crosse County, and when
- Start tipping out standing water weekly by April 6.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 17.
- 3 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
La Crosse County against the rest of WI
La Crosse County has the 1st longest season of 72 WI counties, at 180 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 47.9°F.
- Kenosha County: April 25 to October 21 (179 days, 3 WNV)
- Walworth County: April 23 to October 17 (177 days, 4 WNV)
West Nile in La Crosse County
From 1999 to 2025, CDC ArboNET counted 7 human West Nile cases in La Crosse County (7 neuroinvasive) across 5 years. The worst was 2012 with 3; the latest was 2025.
Background: when the season starts across the US; how the dates are worked out.