Mosquito season in Clackamas County, OR: when it starts and ends
Mosquito months in Clackamas County
In a normal year mosquito season in Clackamas County, OR starts around April 29 and ends around October 17, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Clackamas County, and when
- Start tipping out standing water weekly by April 15.
- Book any yard treatment for late April, ahead of the August peak.
- Repellent can go away after October 17.
- 1 West Nile case since 2016 (last 2018): you should use repellent at dusk August, more so if over 60.
Clackamas County against the rest of OR
Clackamas County has the 20th longest season of 36 OR counties, at 172 days against 225 in Curry County and 95 in Klamath County. Its mean temperature is 50.2°F.
- Tillamook County: May 3 to October 25 (175 days, 0 WNV)
- Benton County: April 27 to October 18 (174 days, 2 WNV)
- Gilliam County: April 26 to October 14 (171 days, 0 WNV)
- Union County: April 26 to October 12 (169 days, 0 WNV)
West Nile in Clackamas County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Clackamas County (2 neuroinvasive) across 2 years. The worst was 2018 with 1; the latest was 2018.
More: how the dates are worked out · when the season starts across the US.