Mosquito season in Garfield County, CO: when it starts and ends
Mosquito months in Garfield County
In a normal year mosquito season in Garfield County, CO starts around June 4 and ends around September 20, about 15 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Garfield County, and when
- Start tipping out standing water weekly by May 21.
- Book any yard treatment for early June, ahead of the July peak.
- Repellent can go away after September 20.
- 2 West Nile cases since 2016 (last 2022): you should use repellent at dusk July, more so if over 60.
Garfield County against the rest of CO
Garfield County has the 51st longest season of 64 CO counties, at 108 days against 200 in Mesa County and 69 in Summit County. Its mean temperature is 40.2°F.
- Eagle County: May 31 to September 18 (110 days, 1 WNV)
- Moffat County: June 1 to September 19 (110 days, 0 WNV)
- Grand County: June 4 to September 15 (102 days, 3 WNV)
- Clear Creek County: June 7 to September 14 (99 days, 2 WNV)
West Nile in Garfield County
From 1999 to 2025, CDC ArboNET counted 17 human West Nile cases in Garfield County (3 neuroinvasive) across 7 years. The worst was 2007 with 5; the latest was 2022.
Background: when mosquitoes go away for the winter; how the dates are worked out.