The weather in San Marcos is characterized by warm Spring times, long, hot, humid Summers, comfortable Fall weather and mild Winters. Summer -Afternoon highs of 90 degrees or more are reached an average of over 120 times each summer. The high humidity is a result of the Gulf of Mexico's moisture and our prevailing winds from the South. Hail will sometimes fall during some of the biggest thunderstorms, but this is rare. Light freezing rain or sleet and a few frosty mornings happen every winter.
Rain is our most common winter precipitation.
By observation, when the temperature drops enough to snow, it usually clears up. Rainfall-The rainfall in San Marcos is often erratic. Rainfall was the highest on record in 1998, due mainly to the flood in October which dumped over 20 inches in 24 hours. 1999 was the opposite being the second driest on record. However, rains typically occur in late spring and early fall, with many thunderstorms in between.