Mosquito season in Mendocino County, CA: when it starts and ends
Mosquito months in Mendocino County
In a normal year mosquito season in Mendocino County, CA starts around March 31 and ends around October 30, about 30 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Mendocino County, and when
- Start tipping out standing water weekly by March 17.
- Book any yard treatment for late March, ahead of the July peak.
- Repellent can go away after October 30.
- No West Nile cases since 2016, so bites in Mendocino County are a nuisance; check window screens.
Mendocino County against the rest of CA
Mendocino County has the 46th longest season of 58 CA counties, at 213 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 55.1°F.
- Placer County: April 3 to November 10 (221 days, 35 WNV)
- Mariposa County: April 4 to November 8 (217 days, 0 WNV)
- Del Norte County: April 5 to November 2 (211 days, 0 WNV)
- Trinity County: April 11 to October 29 (201 days, 0 WNV)
West Nile in Mendocino County
From 1999 to 2025, CDC ArboNET counted 5 human West Nile cases in Mendocino County (5 neuroinvasive) across 3 years. The worst was 2015 with 2; the latest was 2015.
Background: when mosquitoes go away for the winter; how the dates are worked out.