Mosquito season in Glenn County, CA: when it starts and ends
Mosquito months in Glenn County
In a normal year mosquito season in Glenn County, CA starts around March 1 and ends around November 22, about 38 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Glenn County, and when
- Start tipping out standing water weekly by February 15.
- Book any yard treatment for early March, ahead of the July peak.
- Repellent can go away after November 22.
- 18 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to September, and check CA spray notices.
Glenn County against the rest of CA
Glenn County has the 35th longest season of 58 CA counties, at 266 days against 365 in Los Angeles County and 110 in Mono County. Its mean temperature is 60.4°F.
- San Luis Obispo County: February 22 to November 21 (272 days, 6 WNV)
- Calaveras County: March 4 to November 26 (267 days, 2 WNV)
- Madera County: March 4 to November 25 (266 days, 37 WNV)
- Amador County: March 7 to November 23 (261 days, 3 WNV)
West Nile in Glenn County
From 1999 to 2025, CDC ArboNET counted 102 human West Nile cases in Glenn County (30 neuroinvasive) across 19 years. The worst was 2015 with 19; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.