In December, San Marcos typically sees daytime highs of 19.1°C and overnight lows around 5.2°C. Compared to the annual average high of 23.0°C, December runs -4.0°C.
December in San Marcos averages a daytime high of 19.1°C and an overnight low of 5.2°C.
December runs -4.0°C compared to San Marcos's annual average high of 23.0°C, ranking #10 of 12 months by warmth.
Plan for daytime highs near 19.1°C and cooler evenings around 5.2°C.