Mosquito season in Los Angeles County, CA: when it starts and ends
Mosquito months in Los Angeles County
Mosquitoes in Los Angeles County, CA can be active in any month. The worst stretch is June to September.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Los Angeles County, and when
- No off-season here: tip out standing water every week, all year.
- A yard treatment matters most June to September.
- 775 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to September, and check CA spray notices.
Los Angeles County against the rest of CA
Los Angeles County has the 1st longest season of 58 CA counties, at 365 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 65.3°F.
- Orange County: all year (365 days, 117 WNV)
- San Francisco County: all year (365 days, 2 WNV)
West Nile in Los Angeles County
From 1999 to 2025, CDC ArboNET counted 2,262 human West Nile cases in Los Angeles County (1,644 neuroinvasive) across 24 years. The worst was 2004 with 306; the latest was 2025.
More: how the dates are worked out · where mosquitoes never stop.