Mosquito season in Sacramento County, CA: when it starts and ends
Mosquito months in Sacramento County
In a normal year mosquito season in Sacramento County, CA starts around January 29 and ends around December 5, about 44 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Sacramento County, and when
- Start tipping out standing water weekly by January 15.
- Book any yard treatment for late January, ahead of the July peak.
- Repellent can go away after December 5.
- 131 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to September, and check CA spray notices.
Sacramento County against the rest of CA
Sacramento County has the 15th longest season of 58 CA counties, at 310 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 62.6°F.
- Solano County: January 28 to December 7 (313 days, 18 WNV)
- San Bernardino County: January 30 to December 8 (312 days, 122 WNV)
- Stanislaus County: January 30 to December 5 (310 days, 180 WNV)
- Alameda County: February 3 to December 6 (305 days, 4 WNV)
West Nile in Sacramento County
From 1999 to 2025, CDC ArboNET counted 420 human West Nile cases in Sacramento County (224 neuroinvasive) across 21 years. The worst was 2005 with 163; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.