Mosquito season in Tuolumne County, CA: when it starts and ends
Mosquito months in Tuolumne County
In a normal year mosquito season in Tuolumne County, CA starts around May 2 and ends around October 30, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Tuolumne County, and when
- Start tipping out standing water weekly by April 18.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 30.
- 3 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.
Tuolumne County against the rest of CA
Tuolumne County has the 51st longest season of 58 CA counties, at 181 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 51.9°F.
- El Dorado County: April 15 to October 29 (197 days, 6 WNV)
- Siskiyou County: April 16 to October 25 (192 days, 1 WNV)
- Nevada County: May 8 to October 25 (171 days, 3 WNV)
- Modoc County: May 11 to September 25 (137 days, 0 WNV)
West Nile in Tuolumne County
From 1999 to 2025, CDC ArboNET counted 4 human West Nile cases in Tuolumne County (2 neuroinvasive) across 3 years. The worst was 2025 with 2; the latest was 2025.
Background: when the season starts across the US; how the dates are worked out.