Average Weather in January in San Juan Costa Rica
In San Juan, the month of January is characterized by essentially constant daily high temperatures, with daily highs around 78°F throughout the month, rarely exceeding 81°F or dropping below 74°F.
Daily low temperatures are around 63°F, rarely falling below 60°F or exceeding 67°F. The lowest daily average low temperature is 63°F on January 23.
For reference, on April 9, the hottest day of the year, temperatures in San Juan typically range from 64°F to 81°F, while on September 18, the coldest day of the year, they range from 63°F to 77°F.
Average High and Low Temperature in January
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on January. 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 January
The month of January in San Juan experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 36% to 41%. The lowest chance of overcast or mostly cloudy conditions is 36% on January 2.
The clearest day of the month is January 2, with clear, mostly clear, or partly cloudy conditions 64% of the time.
For reference, on June 5, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 96%, while on January 2, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 64%.
Cloud Cover in January
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In San Juan, the chance of a wet day over the course of January is decreasing, starting the month at 13% and ending it at 9%.
For reference, the year's highest daily chance of a wet day is 51% on October 7, and its lowest chance is 7% on March 16.
Probability of Precipitation in January
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 January in San Juan is decreasing, starting the month at 1.5 inches, when it rarely exceeds 3.4 inches or falls below 0.1 inches, and ending the month at 0.9 inches, when it rarely exceeds 2.3 inches.
Average Monthly Rainfall in January
Over the course of January in San Juan, the length of the day is essentially constant. The shortest day of the month is January 1, with 11 hours, 33 minutes of daylight and the longest day is January 31, with 11 hours, 42 minutes of daylight.
Hours of Daylight and Twilight in January
The earliest sunrise of the month in San Juan is 5:53 AM on January 1 and the latest sunrise is 5 minutes later at 5:58 AM on January 27.
The earliest sunset is 5:26 PM on January 1 and the latest sunset is 14 minutes later at 5:40 PM on January 31.
Daylight saving time is not observed in San Juan during 2017.
For reference, on June 21, the longest day of the year, the Sun rises at 5:16 AM and sets 12 hours, 42 minutes later, at 5:59 PM, while on December 21, the shortest day of the year, it rises at 5:48 AM and sets 11 hours, 33 minutes later, at 5:20 PM.
Sunrise & Sunset with Twilight in January
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 in San Juan is gradually decreasing during January, falling from 5% to 3% over the course of the month.
The lowest chance of a muggy day during January is 3% on January 24.
For reference, on June 2, the muggiest day of the year, there are muggy conditions 55% of the time, while on January 24, the least muggy day of the year, there are muggy conditions 3% of the time.
Humidity Comfort Levels in January
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 is essentially constant during January, remaining within 0.1 miles per hour of 1.9 miles per hour throughout.
For reference, on February 5, the windiest day of the year, the daily average wind speed is 2.0 miles per hour, while on September 12, the calmest day of the year, the daily average wind speed is 1.0 miles per hour.
Average Wind Speed in January
Wind Direction in January
San Juan 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 surface water temperature in San Juan is essentially constant during January, remaining around 82°F throughout.
Average Water Temperature in January
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 in San Juan is gradually increasing during January, rising by 0.6 kWh, from 5.5 kWh to 6.1 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in January
For the purposes of this report, the geographical coordinates of San Juan are 9.960 deg latitude, -84.082 deg longitude, and 3,802 ft elevation.
The topography within 2 miles of San Juan contains significant variations in elevation, with a maximum elevation change of 692 feet and an average elevation above sea level of 3,778 feet. Within 10 miles contains significant variations in elevation (5,617 feet). Within 50 miles also contains extreme variations in elevation (11,919 feet).
The area within 2 miles of San Juan is covered by grassland (51%), trees (27%), and artificial surfaces (17%), within 10 miles by trees (44%) and grassland (41%), and within 50 miles by trees (54%) and grassland (17%).
This report illustrates the typical weather in San Juan year round, 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 Juan.
At a distance of 14 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 Tables of the Sun, Moon and Planets , 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 aiports 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.