This report describes the typical weather at the San Antonio International Airport (San Antonio, Texas, United States) weather station over the course of an average year. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
San Antonio, Texas has a warm humid temperate climate with hot summers and no dry season. The area within 25 mi of this station is covered by grasslands (56%), forests (20%), croplands (14%), and built-up areas (9%).
Over the course of a year, the temperature typically varies from 40°F to 95°F and is rarely below 29°F or above 100°F.
The warm season lasts from May 26 to September 21 with an average daily high temperature above 88°F. The hottest day of the year is August 11, with an average high of 95°F and low of 75°F.
The cold season lasts from November 29 to February 18 with an average daily high temperature below 68°F. The coldest day of the year is January 4, with an average low of 40°F and high of 61°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 10:15 hours of daylight; the longest day is June 20 with 14:02 hours of daylight.
The earliest sunrise is at 6:33am on June 10 and the latest sunset is at 8:38pm on July 1. The latest sunrise is at 7:49am on November 3 and the earliest sunset is at 5:34pm on December 2.
Daylight savings time (DST) is observed in this location during 2012, starting in the spring on March 11 and ending in the fall on November 4.
The median cloud cover ranges from 53% (partly cloudy) to 83% (mostly cloudy). The sky is cloudiest on April 10 and clearest on September 4. The clearer part of the year begins around June 9. The cloudier part of the year begins around November 17.
On September 4, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 63% of the time, and overcast or mostly cloudy 35% of the time.
On April 10, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 69% of the time, and clear or mostly clear 29% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around February 28, occurring in 42% of days. Precipitation is least likely around July 27, occurring in 23% of days.
Over the entire year, the most common forms of precipitation are light rain, thunderstorms, moderate rain, and drizzle.
Light rain is the most severe precipitation observed during 33% of those days with precipitation. It is most likely around January 10, when it is observed during 16% of all days.
Thunderstorms are the most severe precipitation observed during 29% of those days with precipitation. They are most likely around May 29, when it is observed during 18% of all days.
Moderate rain is the most severe precipitation observed during 20% of those days with precipitation. It is most likely around January 4, when it is observed during 10% of all days.
Drizzle is the most severe precipitation observed during 14% of those days with precipitation. It is most likely around February 28, when it is observed during 10% of all days.
During the warm season, which lasts from May 26 to September 21, there is a 27% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of thunderstorms (51% of days with precipitation have at worst thunderstorms), light rain (25%), and moderate rain (18%).
During the cold season, which lasts from November 29 to February 18, there is a 39% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light rain (38% of days with precipitation have at worst light rain), moderate rain (24%), drizzle (23%), and thunderstorms (9%).
Either snow is exceptionally unlikely to fall at any time during the year at this location or this station does not reliably report precipitation types.
The relative humidity typically ranges from 38% (comfortable) to 91% (very humid) over the course of the year, rarely dropping below 17% (dry) and reaching as high as 100% (very humid).
The air is driest around August 11, at which time the relative humidity drops below 43% (comfortable) three days out of four; it is most humid around May 23, exceeding 88% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a year, the dew point typically varies from 30°F (dry) to 73°F (very muggy) and is rarely below 16°F (dry) or above 76°F (very muggy).
There are two periods in the year that are most comfortable: The first is between February 18 and April 30 and the second is between September 30 and December 4. The air feels neither too dry nor too muggy during these periods.
Over the course of the year typical wind speeds vary from 0 mph to 16 mph (calm to moderate breeze), rarely exceeding 23 mph (fresh breeze).
The highest average wind speed of 10 mph (gentle breeze) occurs around April 5, at which time the average daily maximum wind speed is 16 mph (moderate breeze).
The lowest average wind speed of 8 mph (light breeze) occurs around September 4, at which time the average daily maximum wind speed is 14 mph (moderate breeze).