Mosquito season in St. Lawrence County, NY: when it starts and ends

Mosquito months in St. Lawrence County

In a normal year mosquito season in St. Lawrence County, NY starts around May 2 and ends around October 9, about 23 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 St. Lawrence County, and when

• Start tipping out standing water weekly by April 18.
• Book any yard treatment for early May, ahead of the July peak.
• Repellent can go away after October 9.
• 3 West Nile cases since 2016 (last 2017): you should use repellent at dusk July, more so if over 60.

St. Lawrence County against the rest of NY

St. Lawrence County has the 47th longest season of 62 NY counties, at 160 days against 218 in New York County and 125 in Franklin County. Its mean temperature is 44.1°F.

• Tioga County: May 2 to October 11 (162 days, 1 WNV)
• Sullivan County: May 2 to October 10 (161 days, 2 WNV)
• Cattaraugus County: May 3 to October 10 (160 days, 1 WNV)
• Madison County: May 3 to October 9 (159 days, 0 WNV)

West Nile in St. Lawrence County

From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in St. Lawrence County (1 neuroinvasive) across 1 year. The worst was 2017 with 3; the latest was 2017.

More: how the dates are worked out · when mosquitoes go away for the winter.