Mosquito season in Jefferson County, TX: when it starts and ends
Mosquito months in Jefferson County
In a normal year mosquito season in Jefferson County, TX starts around January 28 and ends around January 1, about 48 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Jefferson County, and when
- Start tipping out standing water weekly by January 14.
- Book any yard treatment for late January, ahead of the August peak.
- Repellent can go away after January 1.
- 8 West Nile cases since 2016 (last 2020): you should use repellent at dusk May to October, more so if over 60.
Jefferson County against the rest of TX
Jefferson County has the 22nd longest season of 254 TX counties, at 338 days against 365 in Cameron County and 191 in Lipscomb County. Its mean temperature is 69.6°F.
- Harris County: January 27 to January 2 (340 days, 188 WNV)
- Trinity County: February 6 to January 12 (340 days, 2 WNV)
- Fort Bend County: January 26 to December 29 (337 days, 15 WNV)
- Robertson County: February 6 to January 9 (337 days, 0 WNV)
West Nile in Jefferson County
From 1999 to 2025, CDC ArboNET counted 83 human West Nile cases in Jefferson County (53 neuroinvasive) across 13 years. The worst was 2006 with 20; the latest was 2020.
More: how the dates are worked out · where mosquitoes never stop.