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

Mosquito months in Adams County

In a normal year mosquito season in Adams County, PA starts around April 11 and ends around October 27, about 29 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 Adams County, and when

• Start tipping out standing water weekly by March 28.
• Book any yard treatment for mid April, ahead of the July peak.
• Repellent can go away after October 27.
• 2 West Nile cases since 2016 (last 2018): you should use repellent at dusk July to August, more so if over 60.

Adams County against the rest of PA

Adams County has the 8th longest season of 67 PA counties, at 200 days against 222 in Philadelphia County and 154 in Clinton County. Its mean temperature is 52.6°F.

• Bucks County: April 10 to October 31 (204 days, 28 WNV)
• Franklin County: April 8 to October 28 (203 days, 12 WNV)
• Allegheny County: April 12 to October 27 (198 days, 23 WNV)
• Chester County: April 12 to October 27 (198 days, 23 WNV)

West Nile in Adams County

From 1999 to 2025, CDC ArboNET counted 18 human West Nile cases in Adams County (13 neuroinvasive) across 5 years. The worst was 2003 with 13; the latest was 2018.

See how the dates are worked out, and when the season starts across the US.