Mosquito season in Musselshell County, MT: when it starts and ends
Mosquito months in Musselshell County
In a normal year mosquito season in Musselshell County, MT starts around May 7 and ends around October 1, about 21 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Musselshell County, and when
- Start tipping out standing water weekly by April 23.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 1.
- No West Nile cases since 2016, so bites in Musselshell County are a nuisance; check window screens.
Musselshell County against the rest of MT
Musselshell County has the 19th longest season of 56 MT counties, at 147 days against 163 in Dawson County and 89 in Gallatin County. Its mean temperature is 46.2°F.
- Blaine County: May 6 to September 30 (147 days, 4 WNV)
- Broadwater County: May 7 to October 1 (147 days, 1 WNV)
- Petroleum County: May 7 to September 29 (145 days, 0 WNV)
- Pondera County: May 10 to October 2 (145 days, 1 WNV)
West Nile in Musselshell County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Musselshell County (1 neuroinvasive) across 2 years. The worst was 2007 with 1; the latest was 2007.
Background: when mosquitoes go away for the winter; how the dates are worked out.