Mosquito season in La Plata County, CO: when it starts and ends
Mosquito months in La Plata County
In a normal year mosquito season in La Plata County, CO starts around May 7 and ends around October 10, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in La Plata County, and when
- Start tipping out standing water weekly by April 23.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 10.
- 28 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July, and check CO spray notices.
La Plata County against the rest of CO
La Plata County has the 31st longest season of 64 CO counties, at 156 days against 200 in Mesa County and 69 in Summit County. Its mean temperature is 46.7°F.
- Arapahoe County: May 2 to October 10 (161 days, 113 WNV)
- Fremont County: May 2 to October 10 (161 days, 24 WNV)
- Weld County: May 3 to October 5 (155 days, 228 WNV)
- Montrose County: May 11 to October 4 (146 days, 81 WNV)
West Nile in La Plata County
From 1999 to 2025, CDC ArboNET counted 79 human West Nile cases in La Plata County (28 neuroinvasive) across 19 years. The worst was 2004 with 21; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.