Mosquito season in Richland County, WI: when it starts and ends
Mosquito months in Richland County
In a normal year mosquito season in Richland County, WI starts around April 27 and ends around October 12, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Richland 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 Richland County are a nuisance; check window screens.
Richland County against the rest of WI
Richland County has the 20th longest season of 72 WI counties, at 168 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 46°F.
- Waukesha County: April 28 to October 15 (170 days, 15 WNV)
- Marquette County: April 27 to October 12 (168 days, 0 WNV)
- Iowa County: April 27 to October 11 (167 days, 1 WNV)
- Sheboygan County: May 3 to October 17 (166 days, 3 WNV)
West Nile in Richland County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Richland County (0 neuroinvasive) across 1 year. The worst was 2002 with 1; the latest was 2002.
Background: when the season starts across the US; how the dates are worked out.