Mosquito season in Polk County, OR: when it starts and ends
Mosquito months in Polk County
In a normal year mosquito season in Polk County, OR starts around April 22 and ends around October 26, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Polk 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 October 26.
- No West Nile cases since 2016, so bites in Polk County are a nuisance; check window screens.
Polk County against the rest of OR
Polk County has the 12th longest season of 36 OR counties, at 186 days against 225 in Curry County and 95 in Klamath County. Its mean temperature is 51.6°F.
- Washington County: April 16 to October 24 (191 days, 0 WNV)
- Umatilla County: April 14 to October 19 (188 days, 0 WNV)
- Morrow County: April 18 to October 20 (185 days, 0 WNV)
- Linn County: April 22 to October 22 (183 days, 0 WNV)
West Nile in Polk County
CDC ArboNET lists no human West Nile cases for Polk County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 1 of those years.
See how the dates are worked out, and when the season starts across the US.