Mosquito season in Box Elder County, UT: when it starts and ends
Mosquito months in Box Elder County
In a normal year mosquito season in Box Elder County, UT starts around April 30 and ends around October 9, about 23 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Box Elder County, and when
- Start tipping out standing water weekly by April 16.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 9.
- 11 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check UT spray notices.
Box Elder County against the rest of UT
Box Elder County has the 14th longest season of 29 UT counties, at 162 days against 210 in Salt Lake County and 82 in Summit County. Its mean temperature is 47.3°F.
- Tooele County: April 28 to October 12 (167 days, 0 WNV)
- Beaver County: April 30 to October 14 (167 days, 0 WNV)
- Juab County: May 2 to October 9 (160 days, 0 WNV)
- Weber County: May 5 to October 7 (155 days, 15 WNV)
West Nile in Box Elder County
From 1999 to 2025, CDC ArboNET counted 23 human West Nile cases in Box Elder County (11 neuroinvasive) across 8 years. The worst was 2007 with 8; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.