Mosquito season in Westchester County, NY: when it starts and ends

Mosquito months in Westchester County

In a normal year mosquito season in Westchester County, NY starts around April 19 and ends around October 24, about 27 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 Westchester County, and when

• Start tipping out standing water weekly by April 5.
• Book any yard treatment for mid April, ahead of the July peak.
• Repellent can go away after October 24.
• 42 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check NY spray notices.

Westchester County against the rest of NY

Westchester County has the 8th longest season of 62 NY counties, at 188 days against 218 in New York County and 125 in Franklin County. Its mean temperature is 50.6°F.

• Queens County: April 10 to November 7 (211 days, 82 WNV)
• Suffolk County: April 18 to November 1 (197 days, 79 WNV)
• Rockland County: April 20 to October 23 (186 days, 6 WNV)
• Putnam County: April 19 to October 21 (184 days, 0 WNV)

West Nile in Westchester County

From 1999 to 2025, CDC ArboNET counted 85 human West Nile cases in Westchester County (66 neuroinvasive) across 23 years. The worst was 2024 with 12; the latest was 2025.

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