Climate and Average Weather Year Round in San Antonio Costa Rica
In San Antonio, the wet season is muggy and overcast, the dry season is partly cloudy, and it is warm year round. Over the course of the year, the temperature typically varies from 65°F to 84°F and is rarely below 62°F or above 88°F.
Based on the tourism score, the best time of year to visit San Antonio for warm-weather activities is from mid December to mid March.
Climate in San Antonio
Average Temperature in San Antonio
The temperature in San Antonio varies so little throughout the year that it is not entirely meaningful to discuss hot and cold seasons.
Average High and Low Temperature in San Antonio
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, 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 San Antonio
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
In San Antonio, the average percentage of the sky covered by clouds experiences extreme seasonal variation over the course of the year.
The clearer part of the year in San Antonio begins around November 24 and lasts for 4.5 months, ending around April 9. On January 1, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 64% of the time, and overcast or mostly cloudy 36% of the time.
The cloudier part of the year begins around April 9 and lasts for 7.5 months, ending around November 24. On June 5, the cloudiest day of the year, the sky is overcast or mostly cloudy 95% of the time, and clear, mostly clear, or partly cloudy 5% of the time.
Cloud Cover Categories in San Antonio
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in San Antonio varies significantly throughout the year.
The wetter season lasts 6.8 months, from May 4 to November 27, with a greater than 28% chance of a given day being a wet day. The chance of a wet day peaks at 51% on October 7.
The drier season lasts 5.3 months, from November 27 to May 4. The smallest chance of a wet day is 5% on March 16.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 51% on October 7.
Daily Chance of Precipitation in San Antonio
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. San Antonio experiences extreme seasonal variation in monthly rainfall.
Rain falls throughout the year in San Antonio. The most rain falls during the 31 days centered around October 11, with an average total accumulation of 6.5 inches.
The least rain falls around March 15, with an average total accumulation of 0.6 inches.
Average Monthly Rainfall in San Antonio
The length of the day in San Antonio does not vary substantially over the course of the year, staying within 42 minutes of 12 hours throughout. In 2021, the shortest day is December 21, with 11 hours, 33 minutes of daylight; the longest day is June 20, with 12 hours, 43 minutes of daylight.
Hours of Daylight and Twilight in San Antonio
The earliest sunrise is at 5:14 AM on May 28, and the latest sunrise is 45 minutes later at 5:59 AM on January 28. The earliest sunset is at 5:11 PM on November 15, and the latest sunset is 51 minutes later at 6:02 PM on July 11.
Daylight saving time (DST) is not observed in San Antonio during 2021.
Sunrise & Sunset with Twilight in San Antonio
The figure below presents a compact representation of key lunar data for 2021. 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.
Moon Rise, Set & Phases in San Antonio
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.
San Antonio experiences extreme seasonal variation in the perceived humidity.
The muggier period of the year lasts for 7.9 months, from April 15 to December 10, during which time the comfort level is muggy, oppressive, or miserable at least 20% of the time. The muggiest day of the year is June 4, with muggy conditions 69% of the time.
The least muggy day of the year is January 24, with muggy conditions 4% of the time.
Humidity Comfort Levels in San Antonio
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
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 in San Antonio experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 4.1 months, from December 9 to April 11, with average wind speeds of more than 3.0 miles per hour. The windiest day of the year is February 5, with an average hourly wind speed of 4.0 miles per hour.
The calmer time of year lasts for 7.9 months, from April 11 to December 9. The calmest day of the year is September 11, with an average hourly wind speed of 2.0 miles per hour.
Average Wind Speed in San Antonio
The predominant average hourly wind direction in San Antonio varies throughout the year.
The wind is most often from the west for 1.3 months, from September 12 to October 22, with a peak percentage of 38% on September 30. The wind is most often from the east for 11 months, from October 22 to September 12, with a peak percentage of 64% on January 1.
Wind Direction in San Antonio
San Antonio is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average water temperature does not vary significantly over the course of the year, remaining within 1°F of 83°F throughout.
Average Water Temperature in San Antonio
Best Time of Year to Visit
To characterize how pleasant the weather is in San Antonio throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit San Antonio for general outdoor tourist activities is from mid December to mid March, with a peak score in the first week of January.
Tourism Score in San Antonio
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit San Antonio for hot-weather activities is from early December to early April, with a peak score in the first week of January.
Beach/Pool Score in San Antonio
For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.
Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.
Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.
Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.
Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.
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).
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.
Time Spent in Various Temperature Bands and the Growing Season in San Antonio
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
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.
Growing Degree Days in San Antonio
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 experiences significant seasonal variation over the course of the year.
The brighter period of the year lasts for 2.4 months, from February 2 to April 14, with an average daily incident shortwave energy per square meter above 6.2 kWh. The brightest day of the year is March 23, with an average of 6.8 kWh.
The darker period of the year lasts for 5.9 months, from May 20 to November 16, with an average daily incident shortwave energy per square meter below 4.4 kWh. The darkest day of the year is October 11, with an average of 3.8 kWh.
Average Daily Incident Shortwave Solar Energy in San Antonio
For the purposes of this report, the geographical coordinates of San Antonio are 9.983 deg latitude, -84.183 deg longitude, and 3,074 ft elevation.
The topography within 2 miles of San Antonio contains very significant variations in elevation, with a maximum elevation change of 837 feet and an average elevation above sea level of 3,067 feet. Within 10 miles contains very significant variations in elevation (6,545 feet). Within 50 miles also contains extreme variations in elevation (11,447 feet).
The area within 2 miles of San Antonio is covered by grassland (79%) and trees (13%), within 10 miles by grassland (47%) and trees (36%), and within 50 miles by trees (51%) and grassland (17%).
This 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 Point
There is only a single weather station, Juan Santamaría International Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of San Antonio.
At a distance of 3 kilometers from San Antonio, closer than our threshold of 150 kilometers, this station is deemed sufficiently nearby to be relied upon as our primary source for temperature and dew point records.
The station records are corrected for the elevation difference between the 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.
Please note that the station records themselves may additionally have been back-filled using other nearby stations or the MERRA-2 reanalysis.
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 © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.
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.