In September, Sarnia typically sees daytime highs of 22.3°C and overnight lows around 11.1°C. Compared to the annual average high of 13.3°C, September runs +9.0°C.
September in Sarnia averages a daytime high of 22.3°C and an overnight low of 11.1°C.
September runs +9.0°C compared to Sarnia's annual average high of 13.3°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 22.3°C and cooler evenings around 11.1°C.