Mosquito season in Clinton County, PA: when it starts and ends

Mosquito months in Clinton County

In a normal year mosquito season in Clinton County, PA starts around May 7 and ends around October 8, about 22 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 Clinton County, and when

• Start tipping out standing water weekly by April 23.
• Book any yard treatment for early May, ahead of the July peak.
• Repellent can go away after October 8.
• 2 West Nile cases since 2016 (last 2018): you should use repellent at dusk July, more so if over 60.

Clinton County against the rest of PA

Clinton County has the 67th longest season of 67 PA counties, at 154 days against 222 in Philadelphia County and 154 in Clinton County. Its mean temperature is 48.1°F.

• Fayette County: May 5 to October 10 (158 days, 3 WNV)
• Warren County: May 8 to October 11 (156 days, 0 WNV)

West Nile in Clinton County

From 1999 to 2025, CDC ArboNET counted 4 human West Nile cases in Clinton County (4 neuroinvasive) across 3 years. The worst was 2003 with 2; the latest was 2018.

Background: when mosquitoes go away for the winter; how the dates are worked out.