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September Weather at San Antonio International Airport Texas, United States

Daily high temperatures decrease by 7°F, from 93°F to 86°F, rarely falling below 79°F or exceeding 98°F.

Daily low temperatures decrease by 8°F, from 74°F to 66°F, rarely falling below 55°F or exceeding 78°F.

For reference, on August 4, the hottest day of the year, temperatures at San Antonio International Airport typically range from 76°F to 96°F, while on January 6, the coldest day of the year, they range from 43°F to 62°F.

Average High and Low Temperature in September at San Antonio International Airport

Average High and Low Temperature in September at San Antonio International AirportSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303040°F40°F45°F45°F50°F50°F55°F55°F60°F60°F65°F65°F70°F70°F75°F75°F80°F80°F85°F85°F90°F90°F95°F95°F100°F100°FAugOctSep 193°FSep 193°F74°F74°FSep 3086°FSep 3086°F66°F66°FSep 1191°FSep 1191°F72°F72°FSep 2189°FSep 2189°F69°F69°F
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on September. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in September at San Antonio International Airport

Average Hourly Temperature in September at San Antonio International AirportSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMAugOctcoolcomfortablecomfortablewarmhotcool
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Ben Gardane, Tunisia (6,130 miles away); Riāsi, Kashmir, India (8,097 miles); and Rong’an, China (7,864 miles) are the far-away foreign places with temperatures most similar to San Antonio International Airport (view comparison).

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The month of September at San Antonio International Airport experiences decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 42% to 30%.

The clearest day of the month is September 30, with clear, mostly clear, or partly cloudy conditions 70% of the time.

For reference, on January 3, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 46%, while on June 10, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 73%.

Cloud Cover Categories in September at San Antonio International Airport

Cloud Cover Categories in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctSep 158%Sep 158%Sep 3070%Sep 3070%Sep 1162%Sep 1162%Sep 2166%Sep 2166%clearmostly clearpartly cloudymostly cloudyovercast
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At San Antonio International Airport, the chance of a wet day over the course of September is gradually decreasing, starting the month at 25% and ending it at 21%.

For reference, the year's highest daily chance of a wet day is 32% on May 29, and its lowest chance is 13% on December 15.

Probability of Precipitation in September at San Antonio International Airport

Probability of Precipitation in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%0%5%5%10%10%15%15%20%20%25%25%AugOctSep 426%Sep 426%Sep 3021%Sep 3021%Sep 2123%Sep 2123%rain
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during September at San Antonio International Airport is gradually increasing, starting the month at 2.4 inches, when it rarely exceeds 5.6 inches or falls below 0.4 inches, and ending the month at 2.8 inches, when it rarely exceeds 5.9 inches or falls below 0.4 inches.

Average Monthly Rainfall in September at San Antonio International Airport

Average Monthly Rainfall in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 in0 in1 in1 in2 in2 in3 in3 in4 in4 in5 in5 in6 in6 in7 in7 inAugOctSep 12.4 inSep 12.4 inSep 302.8 inSep 302.8 inSep 112.6 inSep 112.6 inSep 212.6 inSep 212.6 in
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.

Over the course of September at San Antonio International Airport, the length of the day is decreasing. From the start to the end of the month, the length of the day decreases by 51 minutes, implying an average daily decrease of 1 minute, 45 seconds, and weekly decrease of 12 minutes, 14 seconds.

The shortest day of the month is September 30, with 11 hours, 53 minutes of daylight and the longest day is September 1, with 12 hours, 44 minutes of daylight.

Hours of Daylight and Twilight in September at San Antonio International Airport

Hours of Daylight and Twilight in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrAugOctSep 2212 hr, 9 minSep 2212 hr, 9 minnightnightdaydaySep 112 hr, 44 minSep 112 hr, 44 min
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month at San Antonio International Airport is 7:11 AM on September 1 and the latest sunrise is 15 minutes later at 7:26 AM on September 30.

The latest sunset is 7:55 PM on September 1 and the earliest sunset is 35 minutes earlier at 7:19 PM on September 30.

Daylight saving time is observed at San Antonio International Airport during 2024, but it neither starts nor ends during September, so the entire month is in daylight saving time.

For reference, on June 20, the longest day of the year, the Sun rises at 6:34 AM and sets 14 hours, 3 minutes later, at 8:36 PM, while on December 21, the shortest day of the year, it rises at 7:24 AM and sets 10 hours, 15 minutes later, at 5:39 PM.

Sunrise & Sunset with Twilight in September at San Antonio International Airport

Sunrise & Sunset with Twilight in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930302 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMAugOct7:11 AM7:11 AMSep 17:55 PMSep 17:55 PM7:26 AM7:26 AMSep 307:19 PMSep 307:19 PM7:16 AM7:16 AMSep 117:43 PMSep 117:43 PMSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of September. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

Solar Elevation and Azimuth in September at San Antonio International Airport

Solar Elevation and Azimuth in September at San Antonio International AirportSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMAugOct001010202020303040405050607000010102020303030404050506060
northeastsouthwest
Solar elevation and azimuth over the course of September 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for September 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

Moon Rise, Set & Phases in September at San Antonio International Airport

Moon Rise, Set & Phases in September at San Antonio International AirportSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMAugOctAug 46:14 AMAug 46:14 AMAug 191:26 PMAug 191:26 PMSep 28:56 PMSep 28:56 PMSep 179:35 PMSep 179:35 PMOct 21:50 PMOct 21:50 PMOct 176:27 AMOct 176:27 AM6:56 AM6:56 AM8:55 PM8:55 PM7:49 PM7:49 PM6:46 AM6:46 AM6:43 AM6:43 AM7:57 PM7:57 PM7:32 PM7:32 PM7:51 AM7:51 AM7:18 AM7:18 AM7:18 PM7:18 PM6:34 PM6:34 PM7:45 AM7:45 AM
The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.
Sep 2024IlluminationMoonriseMoonsetMoonriseMeridian PassingDistance
1
2%5:47 AMENE7:29 PMWNW-12:41 PMS249,233 mi
2
0%6:43 AMENE7:57 PMW-1:22 PMS250,616 mi
3
0%7:37 AME8:23 PMW-2:02 PMS251,638 mi
4
3%8:30 AME8:48 PMW-2:41 PMS252,252 mi
5
7%9:23 AME9:14 PMW-3:19 PMS252,394 mi
6
12%10:16 AMESE9:41 PMWSW-3:58 PMS251,989 mi
7
20%11:10 AMESE10:10 PMWSW-4:40 PMS250,965 mi
8
28%12:06 PMESE10:44 PMWSW-5:25 PMS249,264 mi
9
37%1:04 PMESE11:23 PMWSW-6:13 PMS246,867 mi
10
48%2:04 PMESE--7:06 PMS243,809 mi
11
50%-12:09 AMWSW3:04 PMESE8:03 PMS240,199 mi
12
69%-1:03 AMWSW4:01 PMESE9:03 PMS236,232 mi
13
79%-2:04 AMWSW4:53 PMESE10:02 PMS232,186 mi
14
88%-3:11 AMWSW5:39 PMESE11:01 PMS228,404 mi
15
95%-4:21 AMWSW6:21 PMESE11:56 PMS225,250 mi
16
97%-5:32 AMWSW6:58 PMESE--
17
100%-6:42 AMW7:32 PME12:49 AMS223,055 mi
18
100%-7:51 AMW8:06 PME1:40 AMS222,055 mi
19
98%-9:01 AMW8:41 PMENE2:31 AMS222,350 mi
20
93%-10:11 AMWNW9:19 PMENE3:23 AMS223,880 mi
21
85%-11:22 AMWNW10:01 PMENE4:17 AMS226,448 mi
22
75%-12:33 PMWNW10:48 PMENE5:13 AMS229,752 mi
23
64%-1:40 PMWNW11:42 PMENE6:12 AMS233,455 mi
24
50%-2:41 PMWNW-7:11 AMS237,230 mi
25
42%12:41 AMENE3:35 PMWNW-8:09 AMS240,810 mi
26
32%1:41 AMENE4:20 PMWNW-9:03 AMS244,008 mi
27
23%2:42 AMENE4:59 PMWNW-9:53 AMS246,715 mi
28
15%3:41 AMENE5:32 PMWNW-10:39 AMS248,891 mi
29
8%4:38 AMENE6:01 PMWNW-11:22 AMS250,537 mi
30
4%5:33 AME6:27 PMW-12:02 PMS251,681 mi

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy at San Antonio International Airport is very rapidly decreasing during September, falling from 78% to 45% over the course of the month.

For reference, on July 1, the muggiest day of the year, there are muggy conditions 87% of the time, while on January 16, the least muggy day of the year, there are muggy conditions 2% of the time.

Humidity Comfort Levels in September at San Antonio International Airport

Humidity Comfort Levels in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%AugOctSep 178%Sep 178%Sep 3045%Sep 3045%Sep 1169%Sep 1169%Sep 2157%Sep 2157%oppressiveoppressivemuggymuggyhumidhumiddrydrycomfortablecomfortablemiserablemiserable
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed at San Antonio International Airport is essentially constant during September, remaining within 0.2 miles per hour of 8.1 miles per hour throughout.

For reference, on April 1, the windiest day of the year, the daily average wind speed is 10.5 miles per hour, while on September 4, the calmest day of the year, the daily average wind speed is 7.9 miles per hour.

The lowest daily average wind speed during September is 7.9 miles per hour on September 4.

Average Wind Speed in September at San Antonio International Airport

Average Wind Speed in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 mph0 mph2 mph2 mph4 mph4 mph6 mph6 mph8 mph8 mph10 mph10 mph12 mph12 mph14 mph14 mphAugOctSep 47.9 mphSep 47.9 mphSep 308.4 mphSep 308.4 mphSep 168.1 mphSep 168.1 mph
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The hourly average wind direction at San Antonio International Airport throughout September is predominantly from the south, with a peak proportion of 52% on September 1.

Wind Direction in September at San Antonio International Airport

Wind Direction in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%20%80%40%60%60%40%80%20%100%0%AugOctsoutheastnorthwest
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season at San Antonio International Airport typically lasts for 9.6 months (291 days), from around February 17 to around December 4, rarely starting before January 10 or after March 19, and rarely ending before November 13 or after December 27.

The month of September at San Antonio International Airport is reliably fully within the growing season.

Time Spent in Various Temperature Bands and the Growing Season in September at San Antonio International Airport

Time Spent in Various Temperature Bands and the Growing Season in September at San Antonio International Airportgrowing seasongrowing seasongrowing seasonSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOct100%Sep 16100%Sep 16coolcomfortablewarmhotswelteringcold
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days at San Antonio International Airport are rapidly increasing during September, increasing by 817°F, from 5,098°F to 5,915°F, over the course of the month.

Growing Degree Days in September at San Antonio International Airport

Growing Degree Days in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930304,800°F4,800°F5,000°F5,000°F5,200°F5,200°F5,400°F5,400°F5,600°F5,600°F5,800°F5,800°F6,000°F6,000°F6,200°F6,200°FAugOctSep 15,098°FSep 15,098°FSep 305,915°FSep 305,915°FSep 115,400°FSep 115,400°F
The average growing degree days accumulated over the course of September, with 25th to 75th and 10th to 90th percentile bands.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy at San Antonio International Airport is essentially constant during September, remaining within 0.2 kWh of 5.6 kWh throughout.

Average Daily Incident Shortwave Solar Energy in September at San Antonio International Airport

Average Daily Incident Shortwave Solar Energy in September at San Antonio International AirportSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWhAugOctSep 15.8 kWhSep 15.8 kWhSep 305.4 kWhSep 305.4 kWhSep 115.7 kWhSep 115.7 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

For the purposes of this report, the geographical coordinates of San Antonio International Airport are 29.534 deg latitude, -98.470 deg longitude, and 781 ft elevation.

The topography within 2 miles of San Antonio International Airport contains only modest variations in elevation, with a maximum elevation change of 220 feet and an average elevation above sea level of 780 feet. Within 10 miles contains only modest variations in elevation (764 feet). Within 50 miles contains significant variations in elevation (1,860 feet).

The area within 2 miles of San Antonio International Airport is covered by artificial surfaces (90%), within 10 miles by artificial surfaces (74%) and shrubs (15%), and within 50 miles by shrubs (36%) and cropland (23%).

This report illustrates the typical weather at San Antonio International Airport, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

San Antonio International Airport has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.

In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.

The stations on which we may fall back include but are not limited to Kelly Field Annex, Stinson Municipal Airport, Randolph Air Force Base, New Braunfels Municipal Airport, Pleasanton Municipal Airport, San Marcos Municipal Airport, Hondo Municipal Airport, and Vamc Heliport.

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for airports and weather stations are provided by AskGeo.com .

Maps are © OpenStreetMap contributors.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.

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