Mosquito season in Sanpete County, UT: when it starts and ends

Mosquito months in Sanpete County

In a normal year mosquito season in Sanpete County, UT starts around May 12 and ends around September 29, about 20 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 Sanpete 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 September 29.
• No West Nile cases since 2016, so bites in Sanpete County are a nuisance; check window screens.

Sanpete County against the rest of UT

Sanpete County has the 22nd longest season of 29 UT counties, at 140 days against 210 in Salt Lake County and 82 in Summit County. Its mean temperature is 46.9°F.

• Morgan County: May 10 to October 1 (144 days, 0 WNV)
• Kane County: May 15 to October 5 (143 days, 0 WNV)
• Duchesne County: May 17 to October 1 (137 days, 8 WNV)
• Iron County: May 17 to September 29 (135 days, 0 WNV)

West Nile in Sanpete County

CDC ArboNET lists no human West Nile cases for Sanpete County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 3 of those years.

Background: when the season starts across the US; how the dates are worked out.