Mosquito season in Rio Blanco County, CO: when it starts and ends
Mosquito months in Rio Blanco County
In a normal year mosquito season in Rio Blanco County, CO starts around May 12 and ends around October 1, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Rio Blanco County, and when
- Start tipping out standing water weekly by April 28.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after October 1.
- 4 West Nile cases since 2016 (last 2022): you should use repellent at dusk July, more so if over 60.
Rio Blanco County against the rest of CO
Rio Blanco County has the 34th longest season of 64 CO counties, at 142 days against 200 in Mesa County and 69 in Summit County. Its mean temperature is 44.7°F.
- Weld County: May 3 to October 5 (155 days, 228 WNV)
- Montrose County: May 11 to October 4 (146 days, 81 WNV)
- Jefferson County: May 13 to October 2 (142 days, 132 WNV)
- Costilla County: May 13 to September 30 (140 days, 1 WNV)
West Nile in Rio Blanco County
From 1999 to 2025, CDC ArboNET counted 5 human West Nile cases in Rio Blanco County (3 neuroinvasive) across 4 years. The worst was 2016 with 2; the latest was 2022.
More: how the dates are worked out · reading the West Nile counts.