May in San Marcos averages a daily high of 30.5°C with nights around 18.7°C. Expect roughly 7.8 wet days totalling 114.1mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit San Marcos is February–April.
Based on SAN MARCOS, TX US (0.8km), 1995–2024. 28 years of May data.