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

Mosquito months in Iowa County

In a normal year mosquito season in Iowa County, WI starts around April 27 and ends around October 11, 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 Iowa 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 11.
• 1 West Nile case since 2016 (last 2018): you should use repellent at dusk July to July, more so if over 60.

Iowa County against the rest of WI

Iowa County has the 21st longest season of 72 WI counties, at 167 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 45.8°F.

• Marquette County: April 27 to October 12 (168 days, 0 WNV)
• Richland County: April 27 to October 12 (168 days, 0 WNV)
• Sheboygan County: May 3 to October 17 (166 days, 3 WNV)
• Dodge County: April 29 to October 11 (165 days, 1 WNV)

West Nile in Iowa County

From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Iowa County (2 neuroinvasive) across 3 years. The worst was 2018 with 1; the latest was 2018.

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