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

Mosquito months in Tehama County

In a normal year mosquito season in Tehama County, CA starts around February 7 and ends around November 30, about 42 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 Tehama County, and when

• Start tipping out standing water weekly by January 24.
• Book any yard treatment for early February, ahead of the July peak.
• Repellent can go away after November 30.
• 15 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to September, and check CA spray notices.

Tehama County against the rest of CA

Tehama County has the 25th longest season of 58 CA counties, at 297 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 63.3°F.

• Colusa County: February 5 to December 1 (299 days, 7 WNV)
• Kings County: February 5 to November 30 (298 days, 57 WNV)
• Merced County: February 12 to November 27 (288 days, 60 WNV)
• Ventura County: February 17 to December 1 (287 days, 13 WNV)

West Nile in Tehama County

From 1999 to 2025, CDC ArboNET counted 62 human West Nile cases in Tehama County (27 neuroinvasive) across 16 years. The worst was 2004 with 10; the latest was 2024.

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