Philadelphia sits in a humid subtropical zone (Köppen Cfa), the warmest climate band in Pennsylvania thanks to its low elevation, southeastern position, and the moderating influence of the Delaware and Atlantic. The result is four clearly defined seasons: hot, sticky summers; cool but rarely brutal winters; and a long, pleasant spring and fall that are the best times to be outside in the city.
Summers peak in July, when afternoon highs average the upper 80s and humidity runs high — heat-index days into the 90s and pop-up thunderstorms are routine. Winters bottom out in January, with overnight lows in the upper 20s. Snow is the city's most variable element: a quiet winter might see under a foot, while a single coastal nor'easter can bury Center City in a weekend. Rainfall, by contrast, is spread fairly evenly through the year, with the wettest stretch arriving with summer storms.
The main severe-weather concerns are summer thunderstorms, the rain and wind left behind by tropical systems from August into October, and flooding along the Schuylkill and lower Delaware after heavy or prolonged rain.
Climate normals (approximate)
- Warmest month: July — average high around 87 °F
- Coldest month: January — average low around 27 °F
- Annual precipitation: roughly 41–42 inches
- Annual snowfall: about 22–23 inches (highly variable)
- Climate type: humid subtropical (Köppen Cfa)
Common questions
- When does it snow in Philadelphia?
- Mostly December through March, with January and February the snowiest. Big totals usually come from coastal nor'easters rather than steady winter-long accumulation.
- Does Philadelphia get hurricanes?
- Direct hits are rare. The realistic threat is heavy rain, gusty wind, and flooding from the remnants of tropical systems, generally August through October.
- When is the city most humid?
- Mid-summer — July and August — when high dew points pair with afternoon thunderstorms across the Delaware Valley.
Figures are long-term climate normals (roughly the 1991–2020 reference period) and are meant for context. The live readings at the top of this page always reflect current conditions.