Mosquito season in Iron County, UT: when it starts and ends
Mosquito months in Iron County
In a normal year mosquito season in Iron County, UT starts around May 17 and ends around September 29, about 19 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Iron 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 September 29.
- No West Nile cases since 2016, so bites in Iron County are a nuisance; check window screens.
Iron County against the rest of UT
Iron County has the 24th longest season of 29 UT counties, at 135 days against 210 in Salt Lake County and 82 in Summit County. Its mean temperature is 49.9°F.
- Sanpete County: May 12 to September 29 (140 days, 0 WNV)
- Duchesne County: May 17 to October 1 (137 days, 8 WNV)
- Sevier County: May 26 to September 29 (126 days, 1 WNV)
- Piute County: May 31 to September 23 (115 days, 0 WNV)
West Nile in Iron County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Iron County (0 neuroinvasive) across 2 years. The worst was 2007 with 1; the latest was 2007.
See how the dates are worked out, and when the season starts across the US.