In September, San Mateo typically sees daytime highs of 29.6°C and overnight lows around 18.9°C. Compared to the annual average high of 29.6°C, September runs +0.1°C.
September in San Mateo averages a daytime high of 29.6°C and an overnight low of 18.9°C.
September runs +0.1°C compared to San Mateo's annual average high of 29.6°C, ranking #6 of 12 months by warmth.
Plan for daytime highs near 29.6°C and cooler evenings around 18.9°C.