Mosquito season in Arlington County, VA: when it starts and ends

Mosquito months in Arlington County

In a normal year mosquito season in Arlington County, VA starts around March 30 and ends around November 8, about 32 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 Arlington County, and when

• Start tipping out standing water weekly by March 16.
• Book any yard treatment for late March, ahead of the July peak.
• Repellent can go away after November 8.
• 5 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to September, more so if over 60.

Arlington County against the rest of VA

Arlington County has the 56th longest season of 133 VA counties, at 223 days against 257 in Norfolk city and 172 in Highland County. Its mean temperature is 57.2°F.

• Charlotte County: March 29 to November 7 (223 days, 0 WNV)
• Halifax County: March 29 to November 7 (223 days, 0 WNV)
• Hanover County: March 30 to November 8 (223 days, 1 WNV)
• Nottoway County: March 30 to November 7 (222 days, 0 WNV)

West Nile in Arlington County

From 1999 to 2025, CDC ArboNET counted 19 human West Nile cases in Arlington County (10 neuroinvasive) across 10 years. The worst was 2002 with 4; the latest was 2025.

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