Mosquito season in Chippewa County, WI: when it starts and ends

Mosquito months in Chippewa County

In a normal year mosquito season in Chippewa County, WI starts around April 30 and ends around October 9, about 23 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Chippewa County, and when

• Start tipping out standing water weekly by April 16.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 9.
• 2 West Nile cases since 2016 (last 2025): you should use repellent at dusk July, more so if over 60.

Chippewa County against the rest of WI

Chippewa County has the 34th longest season of 72 WI counties, at 162 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 44.1°F.

• Waushara County: April 30 to October 10 (163 days, 0 WNV)
• Monroe County: April 29 to October 8 (162 days, 2 WNV)
• Dunn County: April 30 to October 9 (162 days, 2 WNV)
• Pepin County: April 30 to October 9 (162 days, 1 WNV)

West Nile in Chippewa County

From 1999 to 2025, CDC ArboNET counted 5 human West Nile cases in Chippewa County (3 neuroinvasive) across 5 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.