January in Philadelphia averages a daily high of 5.4°C with nights around -1.8°C. Expect roughly 10.4 wet days totalling 92.2mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Philadelphia is September–October.
Based on PHILADELPHIA FRANKLIN INSTITUTE, PA US (1km), 1995–2024. 30 years of January data.