This report describes the typical weather at the Lackland Air Force Base (San Antonio, Texas, United States) weather station over the course of an average April. It is based on the historical records from 1991 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 (53%), croplands (24%), forests (13%), and built-up areas (9%).
The month of April is characterized by rising daily high temperatures, with daily highs increasing from 78°F to 85°F over the course of the month, exceeding 93°F or dropping below 69°F only one day in ten.
Over the course of April, the length of the day is gradually increasing. From the start to the end of the month, the length of the day increases by 48 minutes, implying an average day-over-day increase of 1.6 minutes.
The shortest day of the month is April 1 with 12:30 hours of daylight; the longest day is April 30 with 13:18 hours of daylight.
The earliest sunrise is at 6:53am on April 30; the latest sunset is at 8:11pm on April 30; the latest sunrise is at 7:23am on April 1; the earliest sunset is at 7:53pm on April 1.
Daylight saving time is observed in 2012 but it neither starts nor ends in April, so the entire month is in daylight time.
The median cloud cover is 80% (partly cloudy) and does not vary substantially over the course of the month.
On April 15, a representative day, the sky is clear or mostly clear 27% of the time, partly cloudy 12% of the time, and mostly cloudy or overcast 58% of the time.
The average probability that some form of precipitation will be observed in a given day is 41%, with little variation over the course of the month.
Throughout April, the most common forms of precipitation are thunderstorms, light rain, and drizzle.
Thunderstorms are the most severe precipitation observed during 34% of those days with precipitation. They are most likely around April 28, when it is observed during 16% of all days.
Light rain is the most severe precipitation observed during 31% of those days with precipitation. It is most likely around April 7, when it is observed during 14% of all days.
Drizzle is the most severe precipitation observed during 26% of those days with precipitation. It is most likely around April 4, when it is observed during 11% of all days.
Either snow is exceptionally unlikely to fall at this location in April or this station does not reliably report precipitation types.
The relative humidity typically ranges from 43% (comfortable) to 92% (very humid) over the course of a typical April, rarely dropping below 20% (dry) and reaching as high as 100% (very humid).
The air is driest around April 17, at which time the relative humidity drops below 56% (mildly humid) three days out of four; it is most humid around April 26, rising above 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 typical April, the dew point typically varies from 48°F (dry) to 67°F (muggy) and is rarely below 31°F (dry) or above 74°F (very muggy).
The time of the month between April 1 and April 25 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of April typical wind speeds vary from 2 mph to 16 mph (light air to moderate breeze), rarely exceeding 22 mph (fresh breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around April 30, at which time the average daily maximum wind speed is 16 mph (moderate breeze).
The lowest average wind speed of 9 mph (gentle breeze) occurs around April 8, at which time the average daily maximum wind speed is 15 mph (moderate breeze).