Mosquito season in Rock County, WI: when it starts and ends
Mosquito months in Rock County
In a normal year mosquito season in Rock County, WI starts around April 23 and ends around October 16, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Rock 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 16.
- 6 West Nile cases since 2016 (last 2024): you should use repellent at dusk July to August, more so if over 60.
Rock County against the rest of WI
Rock County has the 4th longest season of 72 WI counties, at 176 days against 180 in La Crosse County and 139 in Rusk County. Its mean temperature is 47.5°F.
- Kenosha County: April 25 to October 21 (179 days, 3 WNV)
- Walworth County: April 23 to October 17 (177 days, 4 WNV)
- Milwaukee County: April 28 to October 21 (176 days, 29 WNV)
- Crawford County: April 23 to October 15 (175 days, 2 WNV)
West Nile in Rock County
From 1999 to 2025, CDC ArboNET counted 13 human West Nile cases in Rock County (9 neuroinvasive) across 10 years. The worst was 2016 with 2; the latest was 2024.
More: how the dates are worked out · reading the West Nile counts.