Mosquito season in Prairie County, MT: when it starts and ends
Mosquito months in Prairie County
In a normal year mosquito season in Prairie County, MT starts around May 2 and ends around October 5, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Prairie County, and when
- Start tipping out standing water weekly by April 18.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 5.
- 1 West Nile case since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.
Prairie County against the rest of MT
Prairie County has the 8th longest season of 56 MT counties, at 155 days against 163 in Dawson County and 89 in Gallatin County. Its mean temperature is 44.5°F.
- Richland County: May 2 to October 6 (157 days, 13 WNV)
- Rosebud County: May 3 to October 6 (156 days, 3 WNV)
- Sweet Grass County: May 3 to October 5 (155 days, 1 WNV)
- Lake County: May 4 to October 4 (153 days, 2 WNV)
West Nile in Prairie County
From 1999 to 2025, CDC ArboNET counted 15 human West Nile cases in Prairie County (3 neuroinvasive) across 4 years. The worst was 2003 with 10; the latest was 2023.
More: how the dates are worked out · when the season starts across the US.