Allentown has a humid continental climate , using the 32 degree isotherm. Summers are typically warm and muggy, fall and spring are generally mild, and winter is cool to cold. Precipitation is almost uniformly distributed throughout the year.
The average temperature in January is 30.1 °F (−1.1 °C), and the lowest officially recorded temperature was −15 °F (−26 °C) on January 21, 1994. July averages 75.6 °F (24.2 °C), and the highest temperature on record was 105 °F (41 °C) on July 3, 1966. February is generally the driest month, with only 2.77 inches (70 mm) of average precipitation. Only January averages below freezing, as compared to 2 months with the 1981-2010 normals, seven months average above 50° F (10° C,) and two months average above 22° C (71.6° F.)
Snowfall is variable, with some winters bringing light snow and others bringing numerous significant snowstorms. Average snowfall is 33.1 inches (84 cm) seasonally, with the month of February receiving the highest at just below 11 inches (280 mm). Rainfall is generally spread throughout the year, with eight to twelve wet days per month, at an average annual rate of 43.5 inches (110.5 cm).
Allentown falls under the USDA 6b Plant Hardiness zone.