Mosquito season in Stevens County, WA: when it starts and ends
Mosquito months in Stevens County
In a normal year mosquito season in Stevens County, WA starts around April 30 and ends around September 28, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Stevens 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 September 28.
- No West Nile cases since 2016, so bites in Stevens County are a nuisance; check window screens.
Stevens County against the rest of WA
Stevens County has the 34th longest season of 39 WA counties, at 151 days against 205 in Walla Walla County and 132 in Asotin County. Its mean temperature is 47.2°F.
- Klickitat County: May 2 to October 7 (158 days, 0 WNV)
- King County: May 8 to October 10 (155 days, 8 WNV)
- Pend Oreille County: May 4 to September 28 (147 days, 0 WNV)
- Lincoln County: May 9 to October 1 (145 days, 0 WNV)
West Nile in Stevens County
CDC ArboNET lists no human West Nile cases for Stevens County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 2 of those years.
More: how the dates are worked out · when mosquitoes go away for the winter.