Mosquito season in Teton County, MT: when it starts and ends
Mosquito months in Teton County
In a normal year mosquito season in Teton County, MT starts around May 14 and ends around September 29, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Teton 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 September 29.
- 1 West Nile case since 2016 (last 2018): you should use repellent at dusk July, more so if over 60.
Teton County against the rest of MT
Teton County has the 28th longest season of 56 MT counties, at 139 days against 163 in Dawson County and 89 in Gallatin County. Its mean temperature is 43.4°F.
- Mineral County: May 12 to September 30 (141 days, 0 WNV)
- Park County: May 14 to October 1 (140 days, 1 WNV)
- Liberty County: May 11 to September 26 (138 days, 0 WNV)
- Toole County: May 11 to September 26 (138 days, 4 WNV)
West Nile in Teton County
From 1999 to 2025, CDC ArboNET counted 7 human West Nile cases in Teton County (2 neuroinvasive) across 3 years. The worst was 2007 with 5; the latest was 2018.
More: how the dates are worked out · when the season starts across the US.