Mosquito season in Josephine County, OR: when it starts and ends

Mosquito months in Josephine County

In a normal year mosquito season in Josephine County, OR starts around April 4 and ends around November 1, about 30 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Josephine County, and when

• Start tipping out standing water weekly by March 21.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after November 1.
• No West Nile cases since 2016, so bites in Josephine County are a nuisance; check window screens.

Josephine County against the rest of OR

Josephine County has the 4th longest season of 36 OR counties, at 211 days against 225 in Curry County and 95 in Klamath County. Its mean temperature is 54.9°F.

• Multnomah County: March 30 to November 3 (218 days, 1 WNV)
• Coos County: April 12 to November 10 (212 days, 0 WNV)
• Douglas County: April 7 to October 29 (204 days, 0 WNV)
• Yamhill County: April 10 to October 29 (202 days, 0 WNV)

West Nile in Josephine County

From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Josephine County (0 neuroinvasive) across 1 year. The worst was 2015 with 1; the latest was 2015.

Background: when mosquitoes go away for the winter; how the dates are worked out.