Mosquito season in Beaverhead County, MT: when it starts and ends
Mosquito months in Beaverhead County
In a normal year mosquito season in Beaverhead County, MT starts around May 30 and ends around September 14, about 15 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Beaverhead County, and when
- Start tipping out standing water weekly by May 16.
- Book any yard treatment for late May, ahead of the July peak.
- Repellent can go away after September 14.
- No West Nile cases since 2016, so bites in Beaverhead County are a nuisance; check window screens.
Beaverhead County against the rest of MT
Beaverhead County has the 53rd longest season of 56 MT counties, at 107 days against 163 in Dawson County and 89 in Gallatin County. Its mean temperature is 38.9°F.
- Glacier County: May 30 to September 20 (113 days, 0 WNV)
- Powell County: May 26 to September 11 (108 days, 0 WNV)
- Granite County: May 29 to September 12 (106 days, 0 WNV)
- Sanders County: June 9 to September 18 (101 days, 1 WNV)
West Nile in Beaverhead County
CDC ArboNET lists no human West Nile cases for Beaverhead County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 3 of those years.
More: how the dates are worked out · when mosquitoes go away for the winter.