Mosquito season in Ozaukee County, WI: when it starts and ends
Mosquito months in Ozaukee County
In a normal year mosquito season in Ozaukee County, WI starts around May 6 and ends around October 12, about 23 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Ozaukee County, and when
- Start tipping out standing water weekly by April 22.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 12.
- 2 West Nile cases since 2016 (last 2025): you should use repellent at dusk July, more so if over 60.
Ozaukee County against the rest of WI
Ozaukee County has the 43rd longest season of 72 WI counties, at 160 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 45.1°F.
- Vernon County: April 30 to October 8 (160 days, 0 WNV)
- Portage County: May 1 to October 8 (160 days, 1 WNV)
- Burnett County: May 1 to October 6 (158 days, 0 WNV)
- St. Croix County: May 2 to October 7 (158 days, 4 WNV)
West Nile in Ozaukee County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Ozaukee County (3 neuroinvasive) across 3 years. The worst was 2025 with 1; the latest was 2025.
More: how the dates are worked out · when mosquitoes go away for the winter.