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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.

Average High and Low Temperature

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

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

Average Hourly Temperature at Diego GarciaJanFebMarAprMayJunJulAugSepOctNovDec12 AM4 AM8 AM12 PM4 PM8 PM12 AMhotwarm
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < chilly < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Clouds

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 6.2 months, ending around October 9. 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 9 and lasts for 5.8 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

Cloud Cover Categories at Diego GarciaclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Jul 3038%Jul 3038%Jan 1021%Jan 1021%Apr 329%Apr 329%Oct 929%Oct 929%partly cloudyovercastclearmostly clearmostly cloudy
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

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 21 to March 24, 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 24 to September 21. 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

Daily Chance of Precipitation at Diego GarciawetwetdryJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Jan 2170%Jan 2170%Jul 3128%Jul 3128%Jan 167%Jan 167%Sep 2150%Sep 2150%Mar 2449%Mar 2449%rain
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

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 average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

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 2017, 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

Hours of Daylight and Twilight at Diego GarciaJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 6 minSep 2312 hr, 6 minSep 2312 hr, 33 minDec 2112 hr, 33 minDec 2112 hr, 7 minMar 2012 hr, 7 minMar 2011 hr, 42 minJun 2111 hr, 42 minJun 21daydaynight
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

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 16. 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 30.

Daylight saving time (DST) is not observed at Diego Garcia during 2017.

Sunrise & Sunset with Twilight

Sunrise & Sunset with Twilight at Diego GarciaJanFebMarAprMayJunJulAugSepOctNovDec2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMNov 146:41 AMNov 146:41 AM7:36 PMJan 307:36 PMJan 30May 256:59 PMMay 256:59 PM7:24 AMJul 167:24 AMJul 16daynightnight
The solar day over the course of the year 2017. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Humidity

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

Humidity Comfort Levels at Diego GarciaJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Jul 3197%Jul 3197%100%Nov 24100%Nov 24muggymuggymiserablemiserableoppressiveoppressive
The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

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 significant seasonal variation over the course of the year.

The windier part of the year lasts for 5.0 months, from May 23 to October 24, with average wind speeds of more than 7.0 miles per hour. The windiest day of the year is August 9, with an average hourly wind speed of 9.6 miles per hour.

The calmer time of year lasts for 7.0 months, from October 24 to May 23. The calmest day of the year is April 5, with an average hourly wind speed of 4.6 miles per hour.

Average Wind Speed

Average Wind Speed at Diego GarciawindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph1 mph2 mph3 mph4 mph5 mph6 mph7 mph8 mph9 mph10 mph11 mphAug 99.6 mphAug 99.6 mphApr 54.6 mphApr 54.6 mphMay 237.0 mphMay 237.0 mphOct 247.0 mphOct 247.0 mph
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

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.

Wind Direction

Wind Direction at Diego GarciaWEWJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%westeastsouthnorth
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

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 2.4 months, from February 28 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 2 to September 21, 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

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

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

Average Daily Incident Shortwave Solar Energy at Diego GarciaJanFebMarAprMayJunJulAugSepOctNovDec0 kWh1 kWh2 kWh3 kWh4 kWh5 kWh6 kWh7 kWh8 kWhNov 15.5 kWhNov 15.5 kWhJun 304.6 kWhJun 304.6 kWhAug 195.3 kWhAug 195.3 kWhDec 135.3 kWhDec 135.3 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

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%).

Data Sources

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.

Other Data

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.