Mosquito season in Williamson County, TN: when it starts and ends

Mosquito months in Williamson County

In a normal year mosquito season in Williamson County, TN starts around March 22 and ends around November 10, about 33 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 Williamson County, and when

• Start tipping out standing water weekly by March 8.
• Book any yard treatment for late March, ahead of the July peak.
• Repellent can go away after November 10.
• 1 West Nile case since 2016 (last 2023): you should use repellent at dusk June to September, more so if over 60.

Williamson County against the rest of TN

Williamson County has the 20th longest season of 95 TN counties, at 233 days against 252 in Hamilton County and 186 in Carter County. Its mean temperature is 59.3°F.

• Carroll County: March 21 to November 9 (233 days, 1 WNV)
• Hardeman County: March 21 to November 9 (233 days, 0 WNV)
• Macon County: March 23 to November 11 (233 days, 0 WNV)
• Stewart County: March 23 to November 11 (233 days, 0 WNV)

West Nile in Williamson County

From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Williamson County (2 neuroinvasive) across 2 years. The worst was 2023 with 1; the latest was 2023.

More: how the dates are worked out · when the season starts across the US.