Mosquito season in Glacier County, MT: when it starts and ends
Mosquito months in Glacier County
In a normal year mosquito season in Glacier County, MT starts around May 30 and ends around September 20, about 16 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Glacier 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 20.
- No West Nile cases since 2016, so bites in Glacier County are a nuisance; check window screens.
Glacier County against the rest of MT
Glacier County has the 51st longest season of 56 MT counties, at 113 days against 163 in Dawson County and 89 in Gallatin County. Its mean temperature is 39.6°F.
- Judith Basin County: May 25 to September 18 (116 days, 0 WNV)
- Silver Bow County: May 27 to September 17 (113 days, 0 WNV)
- Powell County: May 26 to September 11 (108 days, 0 WNV)
- Beaverhead County: May 30 to September 14 (107 days, 0 WNV)
West Nile in Glacier County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Glacier County (1 neuroinvasive) across 2 years. The worst was 2007 with 2; the latest was 2007.
See how the dates are worked out, and when mosquitoes go away for the winter.