Mosquito season in Union County, PA: when it starts and ends
Mosquito months in Union County
In a normal year mosquito season in Union County, PA starts around April 15 and ends around October 23, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Union County, and when
- Start tipping out standing water weekly by April 1.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 23.
- 1 West Nile case since 2016 (last 2024): you should use repellent at dusk July to August, more so if over 60.
Union County against the rest of PA
Union County has the 22nd longest season of 67 PA counties, at 191 days against 222 in Philadelphia County and 154 in Clinton County. Its mean temperature is 51°F.
- Perry County: April 14 to October 26 (195 days, 1 WNV)
- Snyder County: April 14 to October 23 (193 days, 0 WNV)
- Mifflin County: April 16 to October 22 (190 days, 0 WNV)
- Beaver County: April 17 to October 23 (189 days, 3 WNV)
West Nile in Union County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Union County (1 neuroinvasive) across 2 years. The worst was 2024 with 1; the latest was 2024.
More: how the dates are worked out · when mosquitoes go away for the winter.