Mosquito season in Montrose County, CO: when it starts and ends
Mosquito months in Montrose County
In a normal year mosquito season in Montrose County, CO starts around May 11 and ends around October 4, about 21 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Montrose County, and when
- Start tipping out standing water weekly by April 27.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after October 4.
- 81 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July, and check CO spray notices.
Montrose County against the rest of CO
Montrose County has the 33rd longest season of 64 CO counties, at 146 days against 200 in Mesa County and 69 in Summit County. Its mean temperature is 44.6°F.
- La Plata County: May 7 to October 10 (156 days, 28 WNV)
- Weld County: May 3 to October 5 (155 days, 228 WNV)
- Rio Blanco County: May 12 to October 1 (142 days, 4 WNV)
- Jefferson County: May 13 to October 2 (142 days, 132 WNV)
West Nile in Montrose County
From 1999 to 2025, CDC ArboNET counted 140 human West Nile cases in Montrose County (69 neuroinvasive) across 16 years. The worst was 2022 with 38; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.