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

Mosquito months in Westmoreland County

In a normal year mosquito season in Westmoreland County, PA starts around April 20 and ends around October 21, about 26 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 Westmoreland County, and when

• Start tipping out standing water weekly by April 6.
• Book any yard treatment for mid April, ahead of the July peak.
• Repellent can go away after October 21.
• 3 West Nile cases since 2016 (last 2020): you should use repellent at dusk July to July, more so if over 60.

Westmoreland County against the rest of PA

Westmoreland County has the 35th longest season of 67 PA counties, at 184 days against 222 in Philadelphia County and 154 in Clinton County. Its mean temperature is 50.3°F.

• Lackawanna County: April 18 to October 21 (186 days, 4 WNV)
• Lycoming County: April 19 to October 20 (184 days, 1 WNV)
• Greene County: April 22 to October 22 (183 days, 0 WNV)
• Centre County: April 20 to October 18 (181 days, 5 WNV)

West Nile in Westmoreland County

From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Westmoreland County (6 neuroinvasive) across 6 years. The worst was 2003 with 4; the latest was 2020.

See how the dates are worked out, and when mosquitoes go away for the winter.