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

Mosquito months in Pacific County

In a normal year mosquito season in Pacific County, WA starts around April 24 and ends around October 20, about 26 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 Pacific County, and when

• Start tipping out standing water weekly by April 10.
• Book any yard treatment for late April, ahead of the August peak.
• Repellent can go away after October 20.
• No West Nile cases since 2016, so bites in Pacific County are a nuisance; check window screens.

Pacific County against the rest of WA

Pacific County has the 15th longest season of 39 WA counties, at 179 days against 205 in Walla Walla County and 132 in Asotin County. Its mean temperature is 50.5°F.

• Clark County: April 21 to October 20 (182 days, 2 WNV)
• Lewis County: April 21 to October 18 (181 days, 0 WNV)
• Thurston County: April 23 to October 18 (178 days, 1 WNV)
• Adams County: April 23 to October 16 (176 days, 0 WNV)

West Nile in Pacific County

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

See how the dates are worked out, and when the season starts across the US.