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

Mosquito months in Summit County

In a normal year mosquito season in Summit County, UT starts around June 19 and ends around September 9, about 12 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 Summit County, and when

• Start tipping out standing water weekly by June 5.
• Book any yard treatment for mid June, ahead of the July peak.
• Repellent can go away after September 9.
• No West Nile cases since 2016, so bites in Summit County are a nuisance; check window screens.

Summit County against the rest of UT

Summit County has the 29th longest season of 29 UT counties, at 82 days against 210 in Salt Lake County and 82 in Summit County. Its mean temperature is 40.7°F.

• Rich County: May 30 to September 11 (104 days, 0 WNV)
• Wasatch County: June 8 to September 20 (104 days, 0 WNV)

West Nile in Summit County

From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Summit County (0 neuroinvasive) across 1 year. The worst was 2012 with 1; the latest was 2012.

Background: when mosquitoes go away for the winter; how the dates are worked out.