Mosquito season in San Benito County, CA: when it starts and ends

Mosquito months in San Benito County

In a normal year mosquito season in San Benito County, CA starts around March 12 and ends around November 22, about 36 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 San Benito 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.
• No West Nile cases since 2016, so bites in San Benito County are a nuisance; check window screens.

San Benito County against the rest of CA

San Benito County has the 39th longest season of 58 CA counties, at 255 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 58.5°F.

• Amador County: March 7 to November 23 (261 days, 3 WNV)
• Monterey County: March 12 to November 22 (255 days, 5 WNV)
• Lake County: March 14 to November 17 (247 days, 10 WNV)
• San Diego County: March 14 to November 14 (245 days, 36 WNV)

West Nile in San Benito County

CDC ArboNET lists no human West Nile cases for San Benito County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 9 of those years.

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