Mosquito season in Campbell County, WY: when it starts and ends
Mosquito months in Campbell County
In a normal year mosquito season in Campbell County, WY starts around May 5 and ends around October 7, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Campbell County, and when
- Start tipping out standing water weekly by April 21.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 7.
- 3 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.
Campbell County against the rest of WY
Campbell County has the 2nd longest season of 23 WY counties, at 155 days against 163 in Big Horn County and 75 in Teton County. Its mean temperature is 46.4°F.
- Big Horn County: April 27 to October 6 (163 days, 1 WNV)
- Fremont County: May 4 to October 4 (153 days, 12 WNV)
- Niobrara County: May 5 to October 5 (153 days, 0 WNV)
West Nile in Campbell County
From 1999 to 2025, CDC ArboNET counted 93 human West Nile cases in Campbell County (26 neuroinvasive) across 10 years. The worst was 2003 with 66; the latest was 2023.
Background: when mosquitoes go away for the winter; how the dates are worked out.