Mosquito season in Malheur County, OR: when it starts and ends
Mosquito months in Malheur County
In a normal year mosquito season in Malheur County, OR starts around May 10 and ends around September 27, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Malheur County, and when
- Start tipping out standing water weekly by April 26.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after September 27.
- 19 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to July, and check OR spray notices.
Malheur County against the rest of OR
Malheur County has the 34th longest season of 36 OR counties, at 140 days against 225 in Curry County and 95 in Klamath County. Its mean temperature is 48.5°F.
- Crook County: May 12 to September 30 (141 days, 0 WNV)
- Grant County: May 13 to October 1 (141 days, 1 WNV)
- Deschutes County: May 19 to October 2 (136 days, 3 WNV)
- Klamath County: June 10 to September 13 (95 days, 3 WNV)
West Nile in Malheur County
From 1999 to 2025, CDC ArboNET counted 135 human West Nile cases in Malheur County (25 neuroinvasive) across 15 years. The worst was 2006 with 53; the latest was 2023.
Background: reading the West Nile counts; how the dates are worked out.