In September, St. Catharines typically sees daytime highs of 21.6°C and overnight lows around 12.4°C. Compared to the annual average high of 12.9°C, September runs +8.7°C.
September in St. Catharines averages a daytime high of 21.6°C and an overnight low of 12.4°C.
September runs +8.7°C compared to St. Catharines's annual average high of 12.9°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 21.6°C and cooler evenings around 12.4°C.