Allentown sits in the Lehigh Valley of eastern Pennsylvania, in a transition zone between humid subtropical and humid continental climates (Köppen Dfa). The valley gives the region four full seasons: warm, humid summers; crisp falls; cold winters with a healthy dose of snow; and a green, changeable spring.
Summers peak in July with highs in the mid-to-upper 80s, humid afternoons, and frequent thunderstorms. Winters are cold — January lows in the low 20s — and snowier than Philadelphia to the south, with the valley averaging around 32 inches a year. Rainfall is generous and fairly even through the seasons, totalling roughly 44 inches.
The Lehigh Valley's main weather hazards are summer thunderstorms and the wind, hail, and downpours they bring; winter ice events along the I-78 corridor; and flooding along the Lehigh River and its tributaries after heavy rain or rapid snowmelt.
Climate normals (approximate)
- Warmest month: July — average high around 86 °F
- Coldest month: January — average low around 22 °F
- Annual precipitation: roughly 44 inches
- Annual snowfall: about 32 inches
- Climate type: humid continental (Köppen Dfa)
Common questions
- How much does it snow in Allentown?
- The Lehigh Valley averages roughly 32 inches of snow a year — more than Philadelphia — mostly between December and March.
- How hot do Allentown summers get?
- July is the warmest month, with average highs in the mid-to-upper 80s and humid afternoons that bring regular thunderstorms.
- Does the Lehigh River flood?
- Yes. Heavy rain or fast snowmelt can push the Lehigh and its tributaries over their banks; low-lying valley areas are the most exposed.
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.