Mosquito season in Johnson County, TX: when it starts and ends

Mosquito months in Johnson County

In a normal year mosquito season in Johnson County, TX starts around March 6 and ends around November 25, about 38 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Johnson County, and when

• Start tipping out standing water weekly by February 20.
• Book any yard treatment for early March, ahead of the August peak.
• Repellent can go away after November 25.
• 17 West Nile cases since 2016: you should wear EPA-registered repellent at dusk May to September, and check TX spray notices.

Johnson County against the rest of TX

Johnson County has the 138th longest season of 254 TX counties, at 264 days against 365 in Cameron County and 191 in Lipscomb County. Its mean temperature is 65°F.

• Harrison County: March 5 to November 24 (264 days, 3 WNV)
• Henderson County: March 5 to November 24 (264 days, 9 WNV)
• Madison County: March 2 to November 20 (263 days, 0 WNV)
• Gillespie County: March 4 to November 22 (263 days, 0 WNV)

West Nile in Johnson County

From 1999 to 2025, CDC ArboNET counted 40 human West Nile cases in Johnson County (30 neuroinvasive) across 12 years. The worst was 2012 with 13; the latest was 2024.

Background: reading the West Nile counts; how the dates are worked out.