Mosquito season in Pend Oreille County, WA: when it starts and ends

Mosquito months in Pend Oreille County

In a normal year mosquito season in Pend Oreille County, WA starts around May 4 and ends around September 28, about 21 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 Pend Oreille County, and when

• Start tipping out standing water weekly by April 20.
• Book any yard treatment for early May, ahead of the July peak.
• Repellent can go away after September 28.
• No West Nile cases since 2016, so bites in Pend Oreille County are a nuisance; check window screens.

Pend Oreille County against the rest of WA

Pend Oreille County has the 35th longest season of 39 WA counties, at 147 days against 205 in Walla Walla County and 132 in Asotin County. Its mean temperature is 45.5°F.

• King County: May 8 to October 10 (155 days, 8 WNV)
• Stevens County: April 30 to September 28 (151 days, 0 WNV)
• Lincoln County: May 9 to October 1 (145 days, 0 WNV)
• Chelan County: May 11 to September 30 (142 days, 0 WNV)

West Nile in Pend Oreille County

CDC ArboNET lists no human West Nile cases for Pend Oreille 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.