Mosquito season in Grant County, OR: when it starts and ends
Mosquito months in Grant County
In a normal year mosquito season in Grant County, OR starts around May 13 and ends around October 1, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Grant County, and when
- Start tipping out standing water weekly by April 29.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after October 1.
- 1 West Nile case since 2016 (last 2017): you should use repellent at dusk July, more so if over 60.
Grant County against the rest of OR
Grant County has the 33rd longest season of 36 OR counties, at 141 days against 225 in Curry County and 95 in Klamath County. Its mean temperature is 46°F.
- Lake County: May 10 to September 28 (141 days, 0 WNV)
- Crook County: May 12 to September 30 (141 days, 0 WNV)
- Malheur County: May 10 to September 27 (140 days, 19 WNV)
- Deschutes County: May 19 to October 2 (136 days, 3 WNV)
West Nile in Grant County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Grant County (1 neuroinvasive) across 1 year. The worst was 2017 with 1; the latest was 2017.
Background: when the season starts across the US; how the dates are worked out.