Mosquito season in Merced County, CA: when it starts and ends
Mosquito months in Merced County
In a normal year mosquito season in Merced County, CA starts around February 12 and ends around November 27, about 41 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Merced County, and when
- Start tipping out standing water weekly by January 29.
- Book any yard treatment for mid February, ahead of the July peak.
- Repellent can go away after November 27.
- 60 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to September, and check CA spray notices.
Merced County against the rest of CA
Merced County has the 26th longest season of 58 CA counties, at 288 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 61.3°F.
- Kings County: February 5 to November 30 (298 days, 57 WNV)
- Tehama County: February 7 to November 30 (297 days, 15 WNV)
- Ventura County: February 17 to December 1 (287 days, 13 WNV)
- Shasta County: February 20 to November 28 (280 days, 16 WNV)
West Nile in Merced County
From 1999 to 2025, CDC ArboNET counted 116 human West Nile cases in Merced County (64 neuroinvasive) across 20 years. The worst was 2005 with 25; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.