Mosquito season in El Dorado County, CA: when it starts and ends
Mosquito months in El Dorado County
In a normal year mosquito season in El Dorado County, CA starts around April 15 and ends around October 29, about 28 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in El Dorado County, and when
- Start tipping out standing water weekly by April 1.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 29.
- 6 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.
El Dorado County against the rest of CA
El Dorado County has the 49th longest season of 58 CA counties, at 197 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 53.9°F.
- Del Norte County: April 5 to November 2 (211 days, 0 WNV)
- Trinity County: April 11 to October 29 (201 days, 0 WNV)
- Siskiyou County: April 16 to October 25 (192 days, 1 WNV)
- Tuolumne County: May 2 to October 30 (181 days, 3 WNV)
West Nile in El Dorado County
From 1999 to 2025, CDC ArboNET counted 13 human West Nile cases in El Dorado County (8 neuroinvasive) across 10 years. The worst was 2023 with 3; the latest was 2023.
Background: reading the West Nile counts; how the dates are worked out.