Mosquito season in Green County, WI: when it starts and ends
Mosquito months in Green County
In a normal year mosquito season in Green County, WI starts around April 23 and ends around October 15, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Green County, and when
- Start tipping out standing water weekly by April 9.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 15.
- 1 West Nile case since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.
Green County against the rest of WI
Green County has the 7th longest season of 72 WI counties, at 175 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 47.3°F.
- Milwaukee County: April 28 to October 21 (176 days, 29 WNV)
- Crawford County: April 23 to October 15 (175 days, 2 WNV)
- Dane County: April 24 to October 15 (174 days, 36 WNV)
- Jefferson County: April 25 to October 16 (174 days, 7 WNV)
West Nile in Green County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Green County (3 neuroinvasive) across 3 years. The worst was 2023 with 1; the latest was 2023.
More: how the dates are worked out · when the season starts across the US.