Mosquito season in Morgan County, CO: when it starts and ends
Mosquito months in Morgan County
In a normal year mosquito season in Morgan County, CO starts around April 27 and ends around October 15, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Morgan County, and when
- Start tipping out standing water weekly by April 13.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 15.
- 23 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check CO spray notices.
Morgan County against the rest of CO
Morgan County has the 16th longest season of 64 CO counties, at 171 days against 200 in Mesa County and 69 in Summit County. Its mean temperature is 49.7°F.
- Delta County: April 25 to October 16 (174 days, 111 WNV)
- Washington County: April 27 to October 16 (172 days, 6 WNV)
- Sedgwick County: April 27 to October 14 (170 days, 4 WNV)
- Montezuma County: April 30 to October 17 (170 days, 10 WNV)
West Nile in Morgan County
From 1999 to 2025, CDC ArboNET counted 134 human West Nile cases in Morgan County (33 neuroinvasive) across 19 years. The worst was 2003 with 61; the latest was 2025.
See how the dates are worked out, and reading the West Nile counts.