December in Harrisburg averages a daily high of 5.2°C with nights around -2.6°C. Expect roughly 10.2 wet days totalling 90.1mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Harrisburg is May–June.
Based on HARRISBURG 1 NE, PA US (1.5km), 1995–2024. 26 years of December data.