Mosquito season in Custer County, CO: when it starts and ends
Mosquito months in Custer County
In a normal year mosquito season in Custer County, CO starts around May 28 and ends around September 20, about 16 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Custer County, and when
- Start tipping out standing water weekly by May 14.
- Book any yard treatment for late May, ahead of the July peak.
- Repellent can go away after September 20.
- 1 West Nile case since 2016 (last 2023): you should use repellent at dusk July, more so if over 60.
Custer County against the rest of CO
Custer County has the 48th longest season of 64 CO counties, at 115 days against 200 in Mesa County and 69 in Summit County. Its mean temperature is 43.3°F.
- Ouray County: May 26 to September 23 (120 days, 0 WNV)
- Teller County: May 27 to September 24 (120 days, 6 WNV)
- Eagle County: May 31 to September 18 (110 days, 1 WNV)
- Moffat County: June 1 to September 19 (110 days, 0 WNV)
West Nile in Custer County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Custer County (0 neuroinvasive) across 2 years. The worst was 2023 with 1; the latest was 2023.
Background: when mosquitoes go away for the winter; how the dates are worked out.