Mosquito season in Crook County, WY: when it starts and ends
Mosquito months in Crook County
In a normal year mosquito season in Crook County, WY starts around May 14 and ends around October 1, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Crook County, and when
- Start tipping out standing water weekly by April 30.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after October 1.
- 1 West Nile case since 2016 (last 2019): you should use repellent at dusk July, more so if over 60.
Crook County against the rest of WY
Crook County has the 15th longest season of 23 WY counties, at 140 days against 163 in Big Horn County and 75 in Teton County. Its mean temperature is 43.3°F.
- Washakie County: May 9 to September 28 (142 days, 3 WNV)
- Johnson County: May 11 to September 30 (142 days, 0 WNV)
- Hot Springs County: May 14 to September 29 (138 days, 1 WNV)
- Carbon County: May 17 to September 26 (132 days, 1 WNV)
West Nile in Crook County
From 1999 to 2025, CDC ArboNET counted 17 human West Nile cases in Crook County (4 neuroinvasive) across 8 years. The worst was 2003 with 9; the latest was 2019.
Background: when mosquitoes go away for the winter; how the dates are worked out.