Mosquito season in Klickitat County, WA: when it starts and ends
Mosquito months in Klickitat County
In a normal year mosquito season in Klickitat County, WA starts around May 2 and ends around October 7, about 23 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Klickitat County, and when
- Start tipping out standing water weekly by April 18.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 7.
- No West Nile cases since 2016, so bites in Klickitat County are a nuisance; check window screens.
Klickitat County against the rest of WA
Klickitat County has the 32nd longest season of 39 WA counties, at 158 days against 205 in Walla Walla County and 132 in Asotin County. Its mean temperature is 47.5°F.
- Douglas County: April 29 to October 9 (163 days, 0 WNV)
- Skamania County: May 3 to October 9 (159 days, 0 WNV)
- King County: May 8 to October 10 (155 days, 8 WNV)
- Stevens County: April 30 to September 28 (151 days, 0 WNV)
West Nile in Klickitat County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Klickitat County (2 neuroinvasive) across 1 year. The worst was 2009 with 2; the latest was 2009.
Background: when mosquitoes go away for the winter; how the dates are worked out.