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

Mosquito months in Washington County

In a normal year mosquito season in Washington County, TN starts around April 7 and ends around November 1, about 30 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 Washington County, and when

• Start tipping out standing water weekly by March 24.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after November 1.
• 3 West Nile cases since 2016 (last 2018): you should use repellent at dusk June to August, more so if over 60.

Washington County against the rest of TN

Washington County has the 84th longest season of 95 TN counties, at 208 days against 252 in Hamilton County and 186 in Carter County. Its mean temperature is 55.8°F.

• Union County: April 7 to November 3 (210 days, 0 WNV)
• Greene County: April 6 to November 1 (209 days, 0 WNV)
• Cannon County: April 5 to October 29 (207 days, 0 WNV)
• Unicoi County: April 7 to October 31 (207 days, 0 WNV)

West Nile in Washington County

From 1999 to 2025, CDC ArboNET counted 6 human West Nile cases in Washington County (4 neuroinvasive) across 6 years. The worst was 2018 with 1; the latest was 2018.

Background: when mosquitoes go away for the winter; how the dates are worked out.