In September, San Marcos typically sees daytime highs of 32.2°C and overnight lows around 19.6°C. Compared to the annual average high of 26.3°C, September runs +5.9°C.
September in San Marcos averages a daytime high of 32.2°C and an overnight low of 19.6°C.
September runs +5.9°C compared to San Marcos's annual average high of 26.3°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 32.2°C and cooler evenings around 19.6°C.