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

Mosquito months in Garfield County

In a normal year mosquito season in Garfield County, WA starts around April 25 and ends around October 12, about 24 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 Garfield County, and when

• Start tipping out standing water weekly by April 11.
• Book any yard treatment for late April, ahead of the August peak.
• Repellent can go away after October 12.
• No West Nile cases since 2016, so bites in Garfield County are a nuisance; check window screens.

Garfield County against the rest of WA

Garfield County has the 22nd longest season of 39 WA counties, at 169 days against 205 in Walla Walla County and 132 in Asotin County. Its mean temperature is 49.2°F.

• Grays Harbor County: April 29 to October 18 (172 days, 0 WNV)
• Skagit County: April 26 to October 14 (171 days, 0 WNV)
• Whitman County: April 26 to October 11 (168 days, 1 WNV)
• Okanogan County: April 24 to October 8 (167 days, 1 WNV)

West Nile in Garfield County

CDC ArboNET lists no human West Nile cases for Garfield County from 1999 to 2025.

More: how the dates are worked out · when mosquitoes go away for the winter.