Mosquito season in Loudoun County, VA: when it starts and ends
Mosquito months in Loudoun County
In a normal year mosquito season in Loudoun County, VA starts around April 4 and ends around November 1, about 30 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Loudoun County, and when
- Start tipping out standing water weekly by March 21.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after November 1.
- 5 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Loudoun County against the rest of VA
Loudoun County has the 82nd longest season of 133 VA counties, at 210 days against 257 in Norfolk city and 172 in Highland County. Its mean temperature is 54.6°F.
- Scott County: April 4 to November 1 (211 days, 0 WNV)
- Warren County: April 4 to November 1 (211 days, 3 WNV)
- Culpeper County: April 5 to November 1 (210 days, 0 WNV)
- Fairfax County: April 5 to November 1 (210 days, 31 WNV)
West Nile in Loudoun County
From 1999 to 2025, CDC ArboNET counted 11 human West Nile cases in Loudoun County (7 neuroinvasive) across 9 years. The worst was 2003 with 2; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.