Average Weather in La Unión El Salvador
In La Unión, the wet season is oppressive and overcast, the dry season is muggy and mostly clear, and it is hot year round. Over the course of the year, the temperature typically varies from 76°F to 95°F and is rarely below 71°F or above 98°F.
Based on the beach/pool score, the best time of year to visit La Unión for hot-weather activities is from early December to mid March.
The temperature in La Unión varies so little throughout the year that it is not entirely meaningful to discuss hot and cold seasons.
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
In La Unión, 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 La Unión begins around November 15 and lasts for 5.0 months, ending around April 14. On January 17, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 80% of the time, and overcast or mostly cloudy 20% of the time.
The cloudier part of the year begins around April 14 and lasts for 7.0 months, ending around November 15. On June 4, the cloudiest day of the year, the sky is overcast or mostly cloudy 92% of the time, and clear, mostly clear, or partly cloudy 8% 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 La Unión varies significantly throughout the year.
The wetter season lasts 5.5 months, from May 10 to October 27, with a greater than 24% chance of a given day being a wet day. The chance of a wet day peaks at 47% on September 11.
The drier season lasts 6.5 months, from October 27 to May 10. The smallest chance of a wet day is 0% on January 14.
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 47% on September 11.
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. La Unión experiences extreme seasonal variation in monthly rainfall.
The rainy period of the year lasts for 7.5 months, from April 10 to November 24, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around September 22, with an average total accumulation of 6.5 inches.
The rainless period of the year lasts for 4.5 months, from November 24 to April 10. The least rain falls around January 14, with an average total accumulation of 0.0 inches.
Average Monthly Rainfall
The length of the day in La Unión varies over the course of the year. In 2020, the shortest day is December 21, with 11 hours, 21 minutes of daylight; the longest day is June 20, with 12 hours, 55 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:23 AM on May 31, and the latest sunrise is 55 minutes later at 6:18 AM on January 23. The earliest sunset is at 5:21 PM on November 19, and the latest sunset is 1 hour, 2 minutes later at 6:22 PM on July 9.
Daylight saving time (DST) is not observed in La Unión during 2020.
Sunrise & Sunset with Twilight
The figure below presents a compact representation of key lunar data for 2020. 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.
La Unión experiences significant seasonal variation in the perceived humidity.
The muggier period of the year lasts for 9.5 months, from March 6 to December 23, during which time the comfort level is muggy, oppressive, or miserable at least 71% of the time. The muggiest day of the year is June 6, with muggy conditions 100% of the time.
The least muggy day of the year is January 27, with muggy conditions 61% of the time.
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 La Unión experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 4.1 months, from November 25 to March 29, with average wind speeds of more than 6.9 miles per hour. The windiest day of the year is January 14, with an average hourly wind speed of 8.4 miles per hour.
The calmer time of year lasts for 7.9 months, from March 29 to November 25. The calmest day of the year is September 9, with an average hourly wind speed of 5.4 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in La Unión varies throughout the year.
The wind is most often from the south for 2.2 months, from April 7 to June 14 and for 2.1 months, from August 19 to October 22, with a peak percentage of 41% on September 12. The wind is most often from the east for 2.2 months, from June 14 to August 19 and for 3.8 months, from December 14 to April 7, with a peak percentage of 57% on July 14. The wind is most often from the north for 1.7 months, from October 22 to December 14, with a peak percentage of 45% on December 1.
La Unión 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 experiences some seasonal variation over the course of the year.
The time of year with warmer water lasts for 4.4 months, from May 15 to September 27, with an average temperature above 85°F. The day of the year with the warmest water is August 18, with an average temperature of 86°F.
The time of year with cooler water lasts for 2.6 months, from December 24 to March 13, with an average temperature below 82°F. The day of the year with the coolest water is January 26, with an average temperature of 82°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in La Unión 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 La Unión for general outdoor tourist activities is from mid December to early March, with a peak score in the second week of January.
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 La Unión for hot-weather activities is from early December to mid March, with a peak score in the third 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).
Temperatures in La Unión 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
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
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 some seasonal variation over the course of the year.
The brighter period of the year lasts for 1.9 months, from February 17 to April 14, with an average daily incident shortwave energy per square meter above 6.6 kWh. The brightest day of the year is March 23, with an average of 7.1 kWh.
The darker period of the year lasts for 1.1 months, from May 15 to June 18, with an average daily incident shortwave energy per square meter below 5.2 kWh. The darkest day of the year is June 3, with an average of 4.7 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of La Unión are 13.337 deg latitude, -87.844 deg longitude, and 52 ft elevation.
The topography within 2 miles of La Unión contains very significant variations in elevation, with a maximum elevation change of 846 feet and an average elevation above sea level of 151 feet. Within 10 miles contains very significant variations in elevation (4,035 feet). Within 50 miles also contains extreme variations in elevation (6,946 feet).
The area within 2 miles of La Unión is covered by water (55%) and cropland (24%), within 10 miles by water (31%) and cropland (24%), and within 50 miles by water (36%) and cropland (23%).
This report illustrates the typical weather in La Unión, 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 are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in La Unión.
For each station, the records are corrected for the elevation difference between that station and La Unión 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 La Unión is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between La Unión and a given station.
The stations contributing to this reconstruction are: Choluteca (57%, 72 kilometers, east); Toncontín International Airport (20%, 105 kilometers, northeast); and Soto Cano Air Base (23%, 119 kilometers, north).
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.