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

Mosquito months in Wahkiakum County

In a normal year mosquito season in Wahkiakum County, WA starts around April 20 and ends around October 24, about 27 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 Wahkiakum County, and when

• Start tipping out standing water weekly by April 6.
• Book any yard treatment for mid April, ahead of the August peak.
• Repellent can go away after October 24.
• No West Nile cases since 2016, so bites in Wahkiakum County are a nuisance; check window screens.

Wahkiakum County against the rest of WA

Wahkiakum County has the 8th longest season of 39 WA counties, at 187 days against 205 in Walla Walla County and 132 in Asotin County. Its mean temperature is 51.3°F.

• Yakima County: April 12 to October 17 (188 days, 4 WNV)
• Grant County: April 12 to October 16 (187 days, 0 WNV)
• Island County: April 17 to October 20 (186 days, 0 WNV)
• San Juan County: April 20 to October 22 (185 days, 0 WNV)

West Nile in Wahkiakum County

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

Background: when mosquitoes go away for the winter; how the dates are worked out.