Mosquito season in Columbia County, OR: when it starts and ends
Mosquito months in Columbia County
In a normal year mosquito season in Columbia County, OR starts around April 25 and ends around October 18, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Columbia County, and when
- Start tipping out standing water weekly by April 11.
- 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 2020): you should use repellent at dusk August, more so if over 60.
Columbia County against the rest of OR
Columbia County has the 17th longest season of 36 OR counties, at 175 days against 225 in Curry County and 95 in Klamath County. Its mean temperature is 50.2°F.
- Jackson County: April 26 to October 24 (181 days, 3 WNV)
- Wasco County: April 24 to October 16 (175 days, 0 WNV)
- Tillamook County: May 3 to October 25 (175 days, 0 WNV)
- Benton County: April 27 to October 18 (174 days, 2 WNV)
West Nile in Columbia County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Columbia County (0 neuroinvasive) across 1 year. The worst was 2020 with 1; the latest was 2020.
More: how the dates are worked out · when the season starts across the US.