Mosquito season in Fergus County, MT: when it starts and ends
Mosquito months in Fergus County
In a normal year mosquito season in Fergus County, MT starts around May 20 and ends around September 28, about 19 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Fergus County, and when
- Start tipping out standing water weekly by May 6.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after September 28.
- No West Nile cases since 2016, so bites in Fergus County are a nuisance; check window screens.
Fergus County against the rest of MT
Fergus County has the 37th longest season of 56 MT counties, at 132 days against 163 in Dawson County and 89 in Gallatin County. Its mean temperature is 42.6°F.
- Wheatland County: May 16 to September 27 (134 days, 0 WNV)
- Wibaux County: May 17 to September 26 (132 days, 0 WNV)
- Roosevelt County: May 14 to September 22 (131 days, 1 WNV)
- Sheridan County: May 15 to September 22 (130 days, 2 WNV)
West Nile in Fergus County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Fergus County (0 neuroinvasive) across 2 years. The worst was 2007 with 1; the latest was 2007.
See how the dates are worked out, and when the season starts across the US.