In September, Green Bay typically sees daytime highs of 21.3°C and overnight lows around 8.9°C. Compared to the annual average high of 12.4°C, September runs +8.9°C.
September in Green Bay averages a daytime high of 21.3°C and an overnight low of 8.9°C.
September runs +8.9°C compared to Green Bay's annual average high of 12.4°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 21.3°C and cooler evenings around 8.9°C.