Mosquito season in Thurston County, WA: when it starts and ends
Mosquito months in Thurston County
In a normal year mosquito season in Thurston County, WA starts around April 23 and ends around October 18, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Thurston County, and when
- Start tipping out standing water weekly by April 9.
- Book any yard treatment for late April, ahead of the August peak.
- Repellent can go away after October 18.
- 1 West Nile case since 2016 (last 2018): you should use repellent at dusk August, more so if over 60.
Thurston County against the rest of WA
Thurston County has the 16th longest season of 39 WA counties, at 178 days against 205 in Walla Walla County and 132 in Asotin County. Its mean temperature is 50.7°F.
- Lewis County: April 21 to October 18 (181 days, 0 WNV)
- Pacific County: April 24 to October 20 (179 days, 0 WNV)
- Adams County: April 23 to October 16 (176 days, 0 WNV)
- Whatcom County: April 25 to October 14 (172 days, 1 WNV)
West Nile in Thurston County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Thurston County (1 neuroinvasive) across 1 year. The worst was 2018 with 1; the latest was 2018.
See how the dates are worked out, and when the season starts across the US.