December Weather in San Antonio ParaguayDaily high temperatures increase by 2°F, from 89°F to 91°F, rarely falling below 81°F or exceeding 97°F. Daily low temperatures increase by 3°F, from 70°F to 73°F, rarely falling below 63°F or exceeding 78°F. For reference, on January 15, the hottest day of the year, temperatures in San Antonio typically range from 73°F to 92°F, while on July 19, the coldest day of the year, they range from 56°F to 73°F. The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on December. 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. Pahokee, Florida, United States (3,929 miles away) and Toolooa, Australia (8,529 miles) are the far-away foreign places with temperatures most similar to San Antonio (view comparison). CloudsThe month of December in San Antonio experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 42% throughout the month. The clearest day of the month is December 10, with clear, mostly clear, or partly cloudy conditions 60% of the time. For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 46%, while on August 31, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 71%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In San Antonio, the chance of a wet day over the course of December is gradually decreasing, starting the month at 37% and ending it at 33%. For reference, the year's highest daily chance of a wet day is 39% on November 14, and its lowest chance is 16% on July 26. RainfallTo 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 December in San Antonio is rapidly decreasing, starting the month at 6.2 inches, when it rarely exceeds 10.5 inches or falls below 2.1 inches, and ending the month at 5.0 inches, when it rarely exceeds 8.0 inches or falls below 1.8 inches. SunOver the course of December in San Antonio, the length of the day is essentially constant. The shortest day of the month is December 1, with 13 hours, 37 minutes of daylight and the longest day is December 20, with 13 hours, 44 minutes of daylight. The earliest sunrise of the month in San Antonio is 5:51 AM on December 1 and the latest sunrise is 11 minutes later at 6:02 AM on December 31. The earliest sunset is 7:27 PM on December 1 and the latest sunset is 16 minutes later at 7:44 PM on December 31. Daylight saving time is observed in San Antonio during 2024, but it neither starts nor ends during December, so the entire month is in standard time. For reference, on December 21, the longest day of the year, the Sun rises at 5:56 AM and sets 13 hours, 44 minutes later, at 7:40 PM, while on June 20, the shortest day of the year, it rises at 6:35 AM and sets 10 hours, 33 minutes later, at 5:08 PM. 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. MoonThe figure below presents a compact representation of key lunar data for December 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.
HumidityWe 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 in San Antonio is rapidly increasing during December, rising from 67% to 80% over the course of the month. For reference, on February 7, the muggiest day of the year, there are muggy conditions 85% of the time, while on August 3, the least muggy day of the year, there are muggy conditions 6% of the time. WindThis 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 in San Antonio is gradually decreasing during December, decreasing from 8.2 miles per hour to 7.6 miles per hour over the course of the month. For reference, on September 7, the windiest day of the year, the daily average wind speed is 9.9 miles per hour, while on March 16, the calmest day of the year, the daily average wind speed is 7.2 miles per hour. The wind direction in San Antonio during December is predominantly out of the east from December 1 to December 16 and the north from December 16 to December 31. Growing SeasonDefinitions 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). Temperatures in San Antonio are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year. 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 in San Antonio are rapidly increasing during December, increasing by 871°F, from 3,085°F to 3,956°F, over the course of the month. Solar EnergyThis 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 in San Antonio is essentially constant during December, remaining around 7.1 kWh throughout. The highest average daily incident shortwave solar energy during December is 7.2 kWh on December 27. TopographyFor the purposes of this report, the geographical coordinates of San Antonio are -25.421 deg latitude, -57.547 deg longitude, and 404 ft elevation. The topography within 2 miles of San Antonio contains only modest variations in elevation, with a maximum elevation change of 463 feet and an average elevation above sea level of 353 feet. Within 10 miles contains only modest variations in elevation (587 feet). Within 50 miles contains significant variations in elevation (1,903 feet). The area within 2 miles of San Antonio is covered by shrubs (32%), cropland (27%), grassland (15%), and trees (14%), within 10 miles by shrubs (30%) and trees (26%), and within 50 miles by trees (36%) and shrubs (31%). Data SourcesThis report illustrates the typical weather in San Antonio, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. Temperature and Dew PointThere are 4 weather stations near enough to contribute to our estimation of the temperature and dew point in San Antonio. For each station, the records are corrected for the elevation difference between that station and San Antonio according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations. The estimated value at San Antonio is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between San Antonio and a given station. The stations contributing to this reconstruction are:
To get a sense of how much these sources agree with each other, you can view a comparison of San Antonio and the stations that contribute to our estimates of its temperature history and climate. Please note that each source's contribution is adjusted for elevation and the relative change present in the MERRA-2 data. Other DataAll 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. DisclaimerThe 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. Please review our full terms contained on our Terms of Service page. |