Mosquito season in District of Columbia, DC: when it starts and ends

Mosquito months in District of Columbia

In a normal year mosquito season in District of Columbia, DC starts around March 26 and ends around November 11, about 33 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 District of Columbia, and when

• Start tipping out standing water weekly by March 12.
• Book any yard treatment for late March, ahead of the July peak.
• Repellent can go away after November 11.
• 45 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to September, and check DC spray notices.

District of Columbia against the rest of DC

West Nile in District of Columbia

From 1999 to 2025, CDC ArboNET counted 141 human West Nile cases in District of Columbia (82 neuroinvasive) across 22 years. The worst was 2002 with 34; the latest was 2025.

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