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

Mosquito months in Sutter County

In a normal year mosquito season in Sutter County, CA starts around February 2 and ends around December 3, about 43 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 Sutter County, and when

• Start tipping out standing water weekly by January 19.
• Book any yard treatment for early February, ahead of the July peak.
• Repellent can go away after December 3.
• 29 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to September, and check CA spray notices.

Sutter County against the rest of CA

Sutter County has the 19th longest season of 58 CA counties, at 304 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 62.9°F.

• Alameda County: February 3 to December 6 (305 days, 4 WNV)
• Contra Costa County: February 8 to December 10 (305 days, 35 WNV)
• Butte County: February 4 to December 3 (303 days, 95 WNV)
• Sonoma County: February 4 to December 4 (302 days, 1 WNV)

West Nile in Sutter County

From 1999 to 2025, CDC ArboNET counted 81 human West Nile cases in Sutter County (31 neuroinvasive) across 16 years. The worst was 2016 with 12; the latest was 2025.

See how the dates are worked out, and reading the West Nile counts.