Excessive Heat in Southern Lycoming, Pennsylvania

Well-above average temperatures, coupled with humid conditions, allowed for multiple days of heat index values over 100 degrees beginning during the afternoon hours of June 22nd and continuing through the late evening hours of June 25, 2025 across southern Lycoming County. Heat index values topped out between 105 and 107 degrees during the afternoon and evening hours of June 23, 2025. Warm and humid conditions continued into the overnight hours throughout this period, offering little relief throughout the time period.

An anomalously strong upper-level ridge began to set up across the eastern contiguous United States, allowing for an extended period of heat across portions of Central Pennsylvania beginning on June 22, 2025. High pressure building to the south on June 23, 2025 allowed for the hottest temperatures and heat index values to occur during the afternoon hours of June 23rd and June 24th across portions of the Susquehanna Valley, highest across the southern tier of Pennsylvania. High pressure began to slowly break down later on in the day of June 24th, allowing for slightly cooling temperatures with an approaching low pressure system from the Ohio Valley allowing for further cooling by June 25, 2025.