Average Weather at Diego Garcia British Indian Ocean Territory
The climate at Diego Garcia is hot, oppressive, windy, and overcast. Over the course of the year, the temperature typically varies from 76°F to 88°F and is rarely below 74°F or above 91°F.
Based on the beach/pool score, the best time of year to visit Diego Garcia for hot-weather activities is from late May to early September.
The temperature at Diego Garcia 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
Mata-Utu, Wallis & Futuna (7,530 miles away); Fagatogo, American Samoa (7,871 miles); and Chichiriviche, Venezuela (9,756 miles) are the far-away foreign places with temperatures most similar to Diego Garcia (view comparison).
At Diego Garcia, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.
The clearer part of the year at Diego Garcia begins around April 3 and lasts for 6.1 months, ending around October 8. On July 30, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 38% of the time, and overcast or mostly cloudy 62% of the time.
The cloudier part of the year begins around October 8 and lasts for 5.9 months, ending around April 3. On January 10, the cloudiest day of the year, the sky is overcast or mostly cloudy 79% of the time, and clear, mostly clear, or partly cloudy 21% 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 at Diego Garcia varies significantly throughout the year.
The wetter season lasts 6.1 months, from September 20 to March 25, with a greater than 49% chance of a given day being a wet day. The chance of a wet day peaks at 70% on January 21.
The drier season lasts 5.9 months, from March 25 to September 20. The smallest chance of a wet day is 28% on July 31.
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 70% on January 21.
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. Diego Garcia experiences extreme seasonal variation in monthly rainfall.
Rain falls throughout the year at Diego Garcia. The most rain falls during the 31 days centered around January 15, with an average total accumulation of 11.1 inches.
The least rain falls around August 3, with an average total accumulation of 2.7 inches.
Average Monthly Rainfall
The length of the day at Diego Garcia does not vary substantially over the course of the year, staying within 33 minutes of 12 hours throughout. In 2021, the shortest day is June 21, with 11 hours, 42 minutes of daylight; the longest day is December 21, with 12 hours, 33 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 6:41 AM on November 14, and the latest sunrise is 43 minutes later at 7:24 AM on July 15. The earliest sunset is at 6:59 PM on May 25, and the latest sunset is 37 minutes later at 7:36 PM on January 29.
Daylight saving time (DST) is not observed at Diego Garcia 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 at Diego Garcia, 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 98% 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 at Diego Garcia experiences extreme seasonal variation over the course of the year.
The windier part of the year lasts for 5.0 months, from May 23 to October 23, with average wind speeds of more than 13.1 miles per hour. The windiest day of the year is August 9, with an average hourly wind speed of 17.7 miles per hour.
The calmer time of year lasts for 7.0 months, from October 23 to May 23. The calmest day of the year is April 5, with an average hourly wind speed of 8.5 miles per hour.
Average Wind Speed
The predominant average hourly wind direction at Diego Garcia varies throughout the year.
The wind is most often from the east for 8.1 months, from April 7 to December 11, with a peak percentage of 74% on June 23. The wind is most often from the west for 3.9 months, from December 11 to April 7, with a peak percentage of 51% on January 1.
Diego Garcia 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 2.3 months, from March 1 to May 10, with an average temperature above 84°F. The day of the year with the warmest water is April 8, with an average temperature of 85°F.
The time of year with cooler water lasts for 2.6 months, from July 3 to September 20, with an average temperature below 81°F. The day of the year with the coolest water is August 12, with an average temperature of 80°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is at Diego Garcia 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 Diego Garcia for general outdoor tourist activities is from early July to early September, with a peak score in the first week of August.
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 Diego Garcia for hot-weather activities is from late May to early September, with a peak score in the first week of August.
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 at Diego Garcia 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 per square meter does not vary significantly over the course of the year, remaining within 0.5 kilowatt-hours of 5.0 kilowatt-hours throughout.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Diego Garcia are -7.313 deg latitude, 72.411 deg longitude, and 0 ft elevation.
The topography within 2 miles of Diego Garcia is essentially flat, with a maximum elevation change of 95 feet and an average elevation above sea level of 3 feet. Within 10 miles is essentially flat (105 feet). Within 50 miles also contains only modest variations in elevation (105 feet).
The area within 2 miles of Diego Garcia is covered by water (100%), within 10 miles by water (100%), and within 50 miles by water (100%).
This report illustrates the typical weather at Diego Garcia, 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
Diego Garcia has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.There are no other weather stations in our network within 200 kilometers of this location. Consequently, in the case of missing or erroneous measurements from this station, we fall back on NASA's MERRA-2 modern-era reanalysis , adjusted according to typical seasonal and diurnal differences between this station and the wide-area MERRA-2 reconstructed values.
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.