Mosquito season in Butler County, PA: when it starts and ends
Mosquito months in Butler County
In a normal year mosquito season in Butler County, PA starts around April 26 and ends around October 17, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Butler County, and when
- Start tipping out standing water weekly by April 12.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 17.
- 1 West Nile case since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.
Butler County against the rest of PA
Butler County has the 46th longest season of 67 PA counties, at 174 days against 222 in Philadelphia County and 154 in Clinton County. Its mean temperature is 48.6°F.
- Clearfield County: April 23 to October 15 (175 days, 0 WNV)
- Indiana County: April 27 to October 19 (175 days, 1 WNV)
- Monroe County: April 24 to October 14 (173 days, 3 WNV)
- Jefferson County: April 25 to October 14 (173 days, 0 WNV)
West Nile in Butler County
From 1999 to 2025, CDC ArboNET counted 6 human West Nile cases in Butler County (4 neuroinvasive) across 3 years. The worst was 2003 with 4; the latest was 2025.
More: how the dates are worked out · when the season starts across the US.