Mosquito season in Duchesne County, UT: when it starts and ends
Mosquito months in Duchesne County
In a normal year mosquito season in Duchesne County, UT starts around May 17 and ends around October 1, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Duchesne County, and when
- Start tipping out standing water weekly by May 3.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after October 1.
- 8 West Nile cases since 2016 (last 2025): you should use repellent at dusk July, more so if over 60.
Duchesne County against the rest of UT
Duchesne County has the 23rd longest season of 29 UT counties, at 137 days against 210 in Salt Lake County and 82 in Summit County. Its mean temperature is 43.7°F.
- Kane County: May 15 to October 5 (143 days, 0 WNV)
- Sanpete County: May 12 to September 29 (140 days, 0 WNV)
- Iron County: May 17 to September 29 (135 days, 0 WNV)
- Sevier County: May 26 to September 29 (126 days, 1 WNV)
West Nile in Duchesne County
From 1999 to 2025, CDC ArboNET counted 23 human West Nile cases in Duchesne County (5 neuroinvasive) across 11 years. The worst was 2005 with 7; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.