In September, San Marcos typically sees daytime highs of 29.1°C and overnight lows around 20.4°C. Compared to the annual average high of 30.2°C, September runs -1.1°C.
September in San Marcos averages a daytime high of 29.1°C and an overnight low of 20.4°C.
September runs -1.1°C compared to San Marcos's annual average high of 30.2°C, ranking #11 of 12 months by warmth.
Plan for daytime highs near 29.1°C and cooler evenings around 20.4°C.