Travel time: Year-round
San Antonio sits in a transitional zone between the humid subtropical climate of East Texas and the semi-arid conditions of the West. This unique positioning creates a climate defined by intense heat and high humidity for much of the year, punctuated by a short, mild winter. The city averages 220 days of sunshine annually, making it a consistently bright, warm destination.
Summer is the dominant and most predictable season in San Antonio. It is characterized by relentless heat and high humidity. Daytime highs regularly reach the mid-to-upper 90s°F (35°C–37°C), frequently surpassing 100°F (38°C) in July and August. Because of the humidity, the "feels like" temperature or heat index often reaches 105°F–110°F. Rainfall is sporadic but often takes the form of brief, intense afternoon thunderstorms driven by Gulf moisture.
Fall is often considered the most pleasant time in the city. Temperatures begin to descend into the 80s°F (27°C–31°C) in October, and by November, daytime highs reach the crisp 70s°F (21°C–26°C). This is one of the secondary rainy seasons, where cold fronts from the north start to clash with warm Gulf air, occasionally resulting in significant rain events.
Winters are short and generally mild, with average highs in the low 60s°F (16°C–18°C). However, the weather can be highly volatile. While many days feel like spring, the region is subject to "Blue Northers"—fast-moving cold fronts that can cause temperatures to drop by 30 or 40 degrees in just a few hours. While rare, freezing rain and light snow have occurred historically, such as the major winter storm of February 2021.
Spring is a season of rapid transition. March begins with mild, pleasant days, but May is statistically the wettest month of the year. This period brings the highest risk of severe weather, including large hail and occasional tornadoes, particularly as the atmosphere becomes more unstable with the return of summer-like heat.
In San Antonio, the day typically starts with high humidity (often 80% or more) and low-hanging clouds known as "stratus" that drift in from the Gulf. By early afternoon, the sun usually burns through these clouds, causing the relative humidity to drop as the temperature climbs rapidly. The late afternoon (4:00 PM to 6:00 PM) is almost always the hottest part of the day, as the land has fully absorbed the sun's radiation.
San Antonio’s topography introduces subtle but important weather variations. The northern part of the city lies on the edge of the Texas Hill Country (the Balcones Escarpment). This area is often 3–5 degrees cooler than the southern part of the city and is more prone to flash flooding. Conversely, the Urban Heat Island effect in downtown San Antonio keeps nighttime temperatures significantly higher than in the surrounding rural outskirts.
San Antonio has a history of extreme weather events, particularly major floods. Because the ground is often hard-packed and clay-like, heavy rain cannot soak in quickly, leading to rapid runoff. Locals have adapted to the heat using "Tex-Mex Air Conditioning"—a combination of ceiling fans, heavy window shading, and a culture of shifting outdoor social activities (like those on the River Walk) to the shaded hours of early morning or late evening.
The most iconic weather event in Central Texas is the Blue Norther. This occurs when a massive mass of cold Canadian air sweeps across the Great Plains and hits the warm Texas air. The name comes from the dark, blue-black clouds that appear on the northern horizon before the wind shifts violently and the temperature plummets, often leaving travelers caught off guard by the sudden transition from summer heat to winter chill.