Mosquito season in Cheyenne County, CO: when it starts and ends

Mosquito months in Cheyenne County

In a normal year mosquito season in Cheyenne County, CO starts around April 28 and ends around October 14, about 24 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Cheyenne County, and when

• Start tipping out standing water weekly by April 14.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 14.
• No West Nile cases since 2016, so bites in Cheyenne County are a nuisance; check window screens.

Cheyenne County against the rest of CO

Cheyenne County has the 19th longest season of 64 CO counties, at 169 days against 200 in Mesa County and 69 in Summit County. Its mean temperature is 50.9°F.

• Sedgwick County: April 27 to October 14 (170 days, 4 WNV)
• Montezuma County: April 30 to October 17 (170 days, 10 WNV)
• Huerfano County: April 29 to October 15 (169 days, 2 WNV)
• Yuma County: April 29 to October 15 (169 days, 3 WNV)

West Nile in Cheyenne County

From 1999 to 2025, CDC ArboNET counted 10 human West Nile cases in Cheyenne County (4 neuroinvasive) across 5 years. The worst was 2003 with 4; the latest was 2014.

See how the dates are worked out, and when the season starts across the US.