Mosquito season in Clatsop County, OR: when it starts and ends
Mosquito months in Clatsop County
In a normal year mosquito season in Clatsop County, OR starts around April 22 and ends around November 1, about 28 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Clatsop County, and when
- Start tipping out standing water weekly by April 8.
- Book any yard treatment for late April, ahead of the August peak.
- Repellent can go away after November 1.
- No West Nile cases since 2016, so bites in Clatsop County are a nuisance; check window screens.
Clatsop County against the rest of OR
Clatsop County has the 9th longest season of 36 OR counties, at 193 days against 225 in Curry County and 95 in Klamath County. Its mean temperature is 51.6°F.
- Lane County: April 16 to October 29 (197 days, 1 WNV)
- Lincoln County: April 27 to November 8 (195 days, 0 WNV)
- Washington County: April 16 to October 24 (191 days, 0 WNV)
- Umatilla County: April 14 to October 19 (188 days, 0 WNV)
West Nile in Clatsop County
CDC ArboNET lists no human West Nile cases for Clatsop County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 1 of those years.
Background: when the season starts across the US; how the dates are worked out.