Mosquito season in Alpine County, CA: when it starts and ends
Mosquito months in Alpine County
In a normal year mosquito season in Alpine County, CA starts around May 28 and ends around October 3, about 18 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Alpine County, and when
- Start tipping out standing water weekly by May 14.
- Book any yard treatment for late May, ahead of the July peak.
- Repellent can go away after October 3.
- No West Nile cases since 2016, so bites in Alpine County are a nuisance; check window screens.
Alpine County against the rest of CA
Alpine County has the 56th longest season of 58 CA counties, at 128 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 44°F.
- Plumas County: May 17 to October 1 (137 days, 0 WNV)
- Sierra County: May 24 to October 5 (133 days, 0 WNV)
- Lassen County: May 30 to October 1 (124 days, 0 WNV)
- Mono County: June 4 to September 22 (110 days, 0 WNV)
West Nile in Alpine County
CDC ArboNET lists no human West Nile cases for Alpine County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 2 of those years.
See how the dates are worked out, and when the season starts across the US.