Mosquito season in Modoc County, CA: when it starts and ends
Mosquito months in Modoc County
In a normal year mosquito season in Modoc County, CA starts around May 11 and ends around September 25, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Modoc County, and when
- Start tipping out standing water weekly by April 27.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after September 25.
- No West Nile cases since 2016, so bites in Modoc County are a nuisance; check window screens.
Modoc County against the rest of CA
Modoc County has the 53rd longest season of 58 CA counties, at 137 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 47.9°F.
- Tuolumne County: May 2 to October 30 (181 days, 3 WNV)
- Nevada County: May 8 to October 25 (171 days, 3 WNV)
- Plumas County: May 17 to October 1 (137 days, 0 WNV)
- Sierra County: May 24 to October 5 (133 days, 0 WNV)
West Nile in Modoc County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Modoc County (2 neuroinvasive) across 1 year. The worst was 2006 with 2; the latest was 2006.
More: how the dates are worked out · when mosquitoes go away for the winter.