Mosquito season in Williamson County, TX: when it starts and ends
Mosquito months in Williamson County
In a normal year mosquito season in Williamson County, TX starts around February 23 and ends around December 5, about 41 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Williamson County, and when
- Start tipping out standing water weekly by February 9.
- Book any yard treatment for late February, ahead of the August peak.
- Repellent can go away after December 5.
- 13 West Nile cases since 2016: you should wear EPA-registered repellent at dusk May to September, and check TX spray notices.
Williamson County against the rest of TX
Williamson County has the 77th longest season of 254 TX counties, at 285 days against 365 in Cameron County and 191 in Lipscomb County. Its mean temperature is 67.2°F.
- Wilson County: February 21 to December 3 (285 days, 1 WNV)
- Wood County: February 22 to December 4 (285 days, 5 WNV)
- Edwards County: February 24 to December 6 (285 days, 0 WNV)
- Brewster County: February 21 to December 2 (284 days, 0 WNV)
West Nile in Williamson County
From 1999 to 2025, CDC ArboNET counted 43 human West Nile cases in Williamson County (24 neuroinvasive) across 11 years. The worst was 2012 with 26; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.