In September, Allentown typically sees daytime highs of 24.4°C and overnight lows around 11.8°C. Compared to the annual average high of 16.2°C, September runs +8.1°C.
September in Allentown averages a daytime high of 24.4°C and an overnight low of 11.8°C.
September runs +8.1°C compared to Allentown's annual average high of 16.2°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 24.4°C and cooler evenings around 11.8°C.