Average Weather in San Juan Argentina
In San Juan, the summers are hot, the winters are cold, and it is dry and mostly clear year round. Over the course of the year, the temperature typically varies from 36°F to 93°F and is rarely below 28°F or above 101°F.
Based on the tourism score, the best times of year to visit San Juan for warm-weather activities are from early February to mid April and from mid October to late December.
The hot season lasts for 3.9 months, from November 14 to March 11, with an average daily high temperature above 87°F. The hottest day of the year is January 8, with an average high of 93°F and low of 69°F.
The cool season lasts for 3.1 months, from May 17 to August 19, with an average daily high temperature below 68°F. The coldest day of the year is July 12, with an average low of 36°F and high of 61°F.
Average High and Low Temperature
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
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
Huachuca City, Arizona, United States (5,155 miles away); Ozona, Texas, United States (4,809 miles); and Monroeville, Alabama, United States (4,532 miles) are the far-away foreign places with temperatures most similar to San Juan (view comparison).
In San Juan, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in San Juan begins around July 30 and lasts for 9.1 months, ending around May 1. On December 9, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 87% of the time, and overcast or mostly cloudy 13% of the time.
The cloudier part of the year begins around May 1 and lasts for 2.9 months, ending around July 30. On June 1, the cloudiest day of the year, the sky is overcast or mostly cloudy 40% of the time, and clear, mostly clear, or partly cloudy 60% of the time.
Cloud Cover Categories
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 Juan varies throughout the year.
The wetter season lasts 2.9 months, from December 20 to March 17, with a greater than 7% chance of a given day being a wet day. The chance of a wet day peaks at 13% on February 20.
The drier season lasts 9.1 months, from March 17 to December 20. The smallest chance of a wet day is 2% on August 6.
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 13% on February 20.
Daily Chance of Precipitation
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 Juan experiences some seasonal variation in monthly rainfall.
The rainy period of the year lasts for 2.9 months, from December 19 to March 15, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around February 14, with an average total accumulation of 1.0 inches.
The rainless period of the year lasts for 9.1 months, from March 15 to December 19. The least rain falls around June 18, with an average total accumulation of 0.1 inches.
Average Monthly Rainfall
The length of the day in San Juan varies significantly over the course of the year. In 2021, the shortest day is June 21, with 10 hours, 5 minutes of daylight; the longest day is December 21, with 14 hours, 13 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 6:21 AM on December 3, and the latest sunrise is 2 hours, 13 minutes later at 8:34 AM on June 30. The earliest sunset is at 6:37 PM on June 11, and the latest sunset is 2 hours, 6 minutes later at 8:43 PM on January 8.
Daylight saving time (DST) is not observed in San Juan during 2021.
Sunrise & Sunset with Twilight
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
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 perceived humidity level in San Juan, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, staying within 2% of 2% throughout.
Humidity Comfort Levels
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 Juan experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 6.6 months, from August 29 to March 17, with average wind speeds of more than 8.0 miles per hour. The windiest day of the year is November 22, with an average hourly wind speed of 9.5 miles per hour.
The calmer time of year lasts for 5.4 months, from March 17 to August 29. The calmest day of the year is June 15, with an average hourly wind speed of 6.4 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in San Juan varies throughout the year.
The wind is most often from the south for 1.3 months, from April 5 to May 14 and for 4.2 months, from July 21 to November 26, with a peak percentage of 34% on October 27. The wind is most often from the west for 2.2 months, from May 14 to July 21, with a peak percentage of 34% on June 28. The wind is most often from the east for 4.3 months, from November 26 to April 5, with a peak percentage of 39% on January 1.
Best Time of Year to Visit
To characterize how pleasant the weather is in San Juan 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 times of year to visit San Juan for general outdoor tourist activities are from early February to mid April and from mid October to late December, with a peak score in the third week of March.
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 Juan for hot-weather activities is from late November to early March, with a peak score in the second week of January.
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).
The growing season in San Juan typically lasts for 9.4 months (285 days), from around August 24 to around June 4, rarely starting before July 31 or after September 18, and rarely ending before May 12 or after June 26.
Time Spent in Various Temperature Bands and the Growing Season
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.
Based on growing degree days alone, the first spring blooms in San Juan should appear around July 27, only rarely appearing before July 22 or after August 4.
Growing Degree Days
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 extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 3.6 months, from October 23 to February 11, with an average daily incident shortwave energy per square meter above 7.7 kWh. The brightest day of the year is December 8, with an average of 8.8 kWh.
The darker period of the year lasts for 3.3 months, from May 2 to August 10, with an average daily incident shortwave energy per square meter below 4.5 kWh. The darkest day of the year is June 14, with an average of 3.4 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of San Juan are -31.538 deg latitude, -68.536 deg longitude, and 2,129 ft elevation.
The topography within 2 miles of San Juan contains only modest variations in elevation, with a maximum elevation change of 180 feet and an average elevation above sea level of 2,116 feet. Within 10 miles contains only modest variations in elevation (3,209 feet). Within 50 miles contains large variations in elevation (12,605 feet).
The area within 2 miles of San Juan is covered by bare soil (75%), within 10 miles by bare soil (31%) and grassland (20%), and within 50 miles by bare soil (32%) and sparse vegetation (24%).
This report illustrates the typical weather in San Juan, 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, Domingo Faustino Sarmiento Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of San Juan.
At a distance of 12 kilometers from San Juan, 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 Juan 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.