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

Mosquito months in Lebanon County

In a normal year mosquito season in Lebanon County, PA starts around April 12 and ends around October 26, about 28 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 Lebanon County, and when

• Start tipping out standing water weekly by March 29.
• Book any yard treatment for mid April, ahead of the July peak.
• Repellent can go away after October 26.
• 14 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check PA spray notices.

Lebanon County against the rest of PA

Lebanon County has the 13th longest season of 67 PA counties, at 197 days against 222 in Philadelphia County and 154 in Clinton County. Its mean temperature is 52.1°F.

• Fulton County: April 12 to October 27 (198 days, 0 WNV)
• Montgomery County: April 12 to October 27 (198 days, 41 WNV)
• Washington County: April 12 to October 25 (196 days, 3 WNV)
• Cumberland County: April 13 to October 26 (196 days, 8 WNV)

West Nile in Lebanon County

From 1999 to 2025, CDC ArboNET counted 29 human West Nile cases in Lebanon County (14 neuroinvasive) across 13 years. The worst was 2018 with 6; the latest was 2025.

Background: reading the West Nile counts; how the dates are worked out.