Mosquito season in Powell County, MT: when it starts and ends
Mosquito months in Powell County
In a normal year mosquito season in Powell County, MT starts around May 26 and ends around September 11, about 15 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Powell County, and when
- Start tipping out standing water weekly by May 12.
- Book any yard treatment for late May, ahead of the July peak.
- Repellent can go away after September 11.
- No West Nile cases since 2016, so bites in Powell County are a nuisance; check window screens.
Powell County against the rest of MT
Powell County has the 52nd longest season of 56 MT counties, at 108 days against 163 in Dawson County and 89 in Gallatin County. Its mean temperature is 39.5°F.
- Silver Bow County: May 27 to September 17 (113 days, 0 WNV)
- Glacier County: May 30 to September 20 (113 days, 0 WNV)
- Beaverhead County: May 30 to September 14 (107 days, 0 WNV)
- Granite County: May 29 to September 12 (106 days, 0 WNV)
West Nile in Powell County
CDC ArboNET lists no human West Nile cases for Powell County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 1 of those years.
See how the dates are worked out, and when mosquitoes go away for the winter.