In September, Waukesha typically sees daytime highs of 21.9°C and overnight lows around 10.6°C. Compared to the annual average high of 12.9°C, September runs +9.1°C.
September in Waukesha averages a daytime high of 21.9°C and an overnight low of 10.6°C.
September runs +9.1°C compared to Waukesha's annual average high of 12.9°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 21.9°C and cooler evenings around 10.6°C.