In September, San Mateo typically sees daytime highs of 30.0°C and overnight lows around 23.7°C. Compared to the annual average high of 30.4°C, September runs -0.4°C.
September in San Mateo averages a daytime high of 30.0°C and an overnight low of 23.7°C.
September runs -0.4°C compared to San Mateo's annual average high of 30.4°C, ranking #7 of 12 months by warmth.
Plan for daytime highs near 30.0°C and cooler evenings around 23.7°C.