Mosquito season in Monterey County, CA: when it starts and ends
Mosquito months in Monterey County
In a normal year mosquito season in Monterey County, CA starts around March 12 and ends around November 22, about 36 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Monterey County, and when
- Start tipping out standing water weekly by February 26.
- Book any yard treatment for mid March, ahead of the August peak.
- Repellent can go away after November 22.
- 5 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to August, more so if over 60.
Monterey County against the rest of CA
Monterey County has the 38th longest season of 58 CA counties, at 255 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 59.4°F.
- Madera County: March 4 to November 25 (266 days, 37 WNV)
- Amador County: March 7 to November 23 (261 days, 3 WNV)
- San Benito County: March 12 to November 22 (255 days, 0 WNV)
- Lake County: March 14 to November 17 (247 days, 10 WNV)
West Nile in Monterey County
From 1999 to 2025, CDC ArboNET counted 7 human West Nile cases in Monterey County (6 neuroinvasive) across 6 years. The worst was 2023 with 2; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.