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

Mosquito months in Prince William County

In a normal year mosquito season in Prince William County, VA starts around April 3 and ends around November 3, about 31 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 Prince William County, and when

• Start tipping out standing water weekly by March 20.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after November 3.
• 7 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.

Prince William County against the rest of VA

Prince William County has the 75th longest season of 133 VA counties, at 214 days against 257 in Norfolk city and 172 in Highland County. Its mean temperature is 55.5°F.

• Fauquier County: April 3 to November 3 (214 days, 1 WNV)
• Franklin County: April 3 to November 3 (214 days, 0 WNV)
• Manassas city: April 3 to November 3 (214 days, 0 WNV)
• Manassas Park city: April 3 to November 3 (214 days, 0 WNV)

West Nile in Prince William County

From 1999 to 2025, CDC ArboNET counted 14 human West Nile cases in Prince William County (8 neuroinvasive) across 11 years. The worst was 2025 with 2; the latest was 2025.

See how the dates are worked out, and reading the West Nile counts.