In September, San Bernardino typically sees daytime highs of 31.9°C and overnight lows around 14.6°C. Compared to the annual average high of 24.7°C, September runs +7.2°C.
September in San Bernardino averages a daytime high of 31.9°C and an overnight low of 14.6°C.
September runs +7.2°C compared to San Bernardino's annual average high of 24.7°C, ranking #3 of 12 months by warmth.
Plan for daytime highs near 31.9°C and cooler evenings around 14.6°C.