Mosquito season in Morrow County, OR: when it starts and ends
Mosquito months in Morrow County
In a normal year mosquito season in Morrow County, OR starts around April 18 and ends around October 20, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Morrow County, and when
- Start tipping out standing water weekly by April 4.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 20.
- No West Nile cases since 2016, so bites in Morrow County are a nuisance; check window screens.
Morrow County against the rest of OR
Morrow County has the 13th longest season of 36 OR counties, at 185 days against 225 in Curry County and 95 in Klamath County. Its mean temperature is 51.6°F.
- Umatilla County: April 14 to October 19 (188 days, 0 WNV)
- Polk County: April 22 to October 26 (186 days, 0 WNV)
- Linn County: April 22 to October 22 (183 days, 0 WNV)
- Jackson County: April 26 to October 24 (181 days, 3 WNV)
West Nile in Morrow County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Morrow County (0 neuroinvasive) across 1 year. The worst was 2009 with 1; the latest was 2009.
Background: when the season starts across the US; how the dates are worked out.