In September, Rennes typically sees daytime highs of 20.9°C and overnight lows around 10.5°C. Compared to the annual average high of 15.3°C, September runs +5.5°C.
September in Rennes averages a daytime high of 20.9°C and an overnight low of 10.5°C.
September runs +5.5°C compared to Rennes's annual average high of 15.3°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 20.9°C and cooler evenings around 10.5°C.