Mosquito season in Fairfax County, VA: when it starts and ends
Mosquito months in Fairfax County
In a normal year mosquito season in Fairfax County, VA starts around April 5 and ends around November 1, about 30 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Fairfax County, and when
- Start tipping out standing water weekly by March 22.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after November 1.
- 31 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to August, and check VA spray notices.
Fairfax County against the rest of VA
Fairfax County has the 84th longest season of 133 VA counties, at 210 days against 257 in Norfolk city and 172 in Highland County. Its mean temperature is 54.4°F.
- Loudoun County: April 4 to November 1 (210 days, 5 WNV)
- Culpeper County: April 5 to November 1 (210 days, 0 WNV)
- Rappahannock County: April 5 to November 1 (210 days, 1 WNV)
- Nelson County: April 5 to October 31 (209 days, 0 WNV)
West Nile in Fairfax County
From 1999 to 2025, CDC ArboNET counted 77 human West Nile cases in Fairfax County (47 neuroinvasive) across 19 years. The worst was 2002 with 13; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.