Weather in San Antonio

San Antonio is in United States at 29.4°N. The 2001–2020 NASA POWER daily record describes a humid subtropical climate. Rain is about 780 mm of rain spread through the year. The wettest month is May at 100 mm; the driest is February at 36 mm.

August is the warmest month (average 30.0°C, high 36.1°C) and January is the coolest (average 10.8°C, low 4.5°C). From the coolest night in January (4.5°C) to the hottest afternoon in August (36.1°C), the raw range is 31.6°C. On this site the months that score closest to a 22°C day, lighter rain, and moderate humidity are April, May, and October.

Temperature through the year

Monthly average highs run from 17.0°C in January to 36.1°C in August. Nights follow the same curve: 4.5°C in January and 23.9°C in August.

Mean high across all twelve months is 27.3°C and mean low is 14.7°C. These are 20-year grid averages, so a city station can read a few degrees warmer or cooler.

Rain through the year

Annual rainfall is 780 mm. May leads at 100 mm; February is lightest at 36 mm.

A rainy day here is a day with at least 1 mm in the NASA POWER series. May averages 10 such days; February averages 5.

Distinctive months in San Antonio

January is the coolest month, with lows around 4.5°C and highs near 17.0°C. Rainfall is 49 mm. February is the driest month, averaging only 36 mm across 5 rainy days. Highs sit near 19.7°C. March stands apart from the months beside it: 24.0°C / 10.5°C and 62 mm. April: 28.4°C high, 14.6°C low, 62 mm rain, 66% humidity. May is the wettest month — 100 mm and 10 rainy days, with 68% humidity.

Peak heat arrives in August: 36.1°C by day, 23.9°C at night, and 61% humidity. In September, San Antonio averages 32.2°C by day and 20.9°C at night, with 95 mm of rain. In October, San Antonio averages 28.3°C by day and 15.5°C at night, with 79 mm of rain. November: 22.6°C high, 10.1°C low, 49 mm rain, 70% humidity. December stands apart from the months beside it: 18.0°C / 5.5°C and 45 mm.

Best months to visit San Antonio

The three months with the highest comfort score are April, May, and October: April (21.5°C average, 62 mm, 66% humidity); May (25.3°C average, 100 mm, 68% humidity); October (21.9°C average, 79 mm, 68% humidity). They fall in calendar order. The score rewards averages near 22°C, lower rainfall, and humidity near 60%. It is a climate score, not a festival or price calendar.

If you prefer the hottest stretch, that is August. The coolest stretch is January.

How San Antonio compares inside United States

Houston is about 305 km away: San Antonio is about as warm as Houston at the hot peak and 467 mm drier over the year than Houston. Houston’s wettest month is October (128 mm) versus May here.

Dallas is about 407 km away: San Antonio is about as warm as Dallas at the hot peak and 143 mm drier over the year than Dallas. Dallas’s wettest month is May (116 mm) versus May here.

Phoenix is about 1363 km away: San Antonio is 3.9°C cooler than Phoenix in its hottest month and 523 mm wetter over the year than Phoenix. Phoenix’s wettest month is August (34 mm) versus May here.