In September, Gaithersburg typically sees daytime highs of 26.3°C and overnight lows around 13.6°C. Compared to the annual average high of 18.5°C, September runs +7.7°C.
September in Gaithersburg averages a daytime high of 26.3°C and an overnight low of 13.6°C.
September runs +7.7°C compared to Gaithersburg's annual average high of 18.5°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 26.3°C and cooler evenings around 13.6°C.