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

Mosquito months in Marquette County

In a normal year mosquito season in Marquette County, WI starts around April 27 and ends around October 12, about 24 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 Marquette County, and when

• Start tipping out standing water weekly by April 13.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 12.
• No West Nile cases since 2016, so bites in Marquette County are a nuisance; check window screens.

Marquette County against the rest of WI

Marquette County has the 19th longest season of 72 WI counties, at 168 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 45.8°F.

• Winnebago County: April 27 to October 14 (170 days, 2 WNV)
• Waukesha County: April 28 to October 15 (170 days, 15 WNV)
• Richland County: April 27 to October 12 (168 days, 0 WNV)
• Iowa County: April 27 to October 11 (167 days, 1 WNV)

West Nile in Marquette County

From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Marquette County (1 neuroinvasive) across 1 year. The worst was 2002 with 1; the latest was 2002.

Background: when mosquitoes go away for the winter; how the dates are worked out.