Climate and Average Weather Year Round in British Indian Ocean Territory British Indian Ocean Territory

The climate in British Indian Ocean Territory 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 British Indian Ocean Territory for hot-weather activities is from late May to early September.

The temperature in British Indian Ocean Territory varies so little throughout the year that it is not entirely meaningful to discuss hot and cold seasons.

In British Indian Ocean Territory, 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 in British Indian Ocean Territory begins around April 2 and lasts for 6.1 months, ending around October 7.

The clearest month of the year in British Indian Ocean Territory is July, during which on average the sky is clear, mostly clear, or partly cloudy 37% of the time.

The cloudier part of the year begins around October 7 and lasts for 5.9 months, ending around April 2.

The cloudiest month of the year in British Indian Ocean Territory is January, during which on average the sky is overcast or mostly cloudy 79% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in British Indian Ocean Territory varies significantly throughout the year.

The wetter season lasts 6.1 months, from September 19 to March 24, with a greater than 49% chance of a given day being a wet day. The month with the most wet days in British Indian Ocean Territory is January, with an average of 21.1 days with at least 0.04 inches of precipitation.

The drier season lasts 5.9 months, from March 24 to September 19. The month with the fewest wet days in British Indian Ocean Territory is July, with an average of 9.7 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in British Indian Ocean Territory is January, with an average of 21.1 days. 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.

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. British Indian Ocean Territory experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year in British Indian Ocean Territory. The month with the most rain in British Indian Ocean Territory is January, with an average rainfall of 11.1 inches.

The month with the least rain in British Indian Ocean Territory is July, with an average rainfall of 3.0 inches.

The length of the day in British Indian Ocean Territory does not vary substantially over the course of the year, staying within 28 minutes of 12 hours throughout. In 2024, the shortest day is June 21, with 11 hours, 47 minutes of daylight; the longest day is December 21, with 12 hours, 28 minutes of daylight.

The earliest sunrise is at 6:44 AM on November 12, and the latest sunrise is 39 minutes later at 7:23 AM on July 17. The earliest sunset is at 7:03 PM on May 22, and the latest sunset is 33 minutes later at 7:36 PM on February 1.

Daylight saving time (DST) is not observed in British Indian Ocean Territory during 2024.

The figure below presents a compact representation of key lunar data for 2024. 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.

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 British Indian Ocean Territory, 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.

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 British Indian Ocean Territory experiences extreme seasonal variation over the course of the year.

The windier part of the year lasts for 5.0 months, from May 22 to October 22, with average wind speeds of more than 13.1 miles per hour. The windiest month of the year in British Indian Ocean Territory is August, with an average hourly wind speed of 17.5 miles per hour.

The calmer time of year lasts for 7.0 months, from October 22 to May 22. The calmest month of the year in British Indian Ocean Territory is March, with an average hourly wind speed of 9.0 miles per hour.

The predominant average hourly wind direction in British Indian Ocean Territory varies throughout the year.

The wind is most often from the east for 8.1 months, from April 6 to December 10, with a peak percentage of 74% on June 22. The wind is most often from the west for 3.9 months, from December 10 to April 6, with a peak percentage of 51% on January 1.

British Indian Ocean Territory 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 29 to May 9, with an average temperature above 84°F. The month of the year in British Indian Ocean Territory with the warmest water is April, with an average temperature of 84°F.

The time of year with cooler water lasts for 2.6 months, from July 2 to September 19, with an average temperature below 81°F. The month of the year in British Indian Ocean Territory with the coolest water is August, with an average temperature of 80°F.

To characterize how pleasant the weather is in British Indian Ocean Territory 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 British Indian Ocean Territory 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 British Indian Ocean Territory for hot-weather activities is from late May to early September, with a peak score in the last week of July.

Methodology

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 British Indian Ocean Territory 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.

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.

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.

For the purposes of this report, the geographical coordinates of British Indian Ocean Territory are -6.000 deg latitude, 72.000 deg longitude, and 0 ft elevation.

The topography within 2 miles of British Indian Ocean Territory is essentially flat, with a maximum elevation change of 0 feet and an average elevation above sea level of 0 feet. Within 10 miles is also essentially flat (0 feet). Within 50 miles is also essentially flat (0 feet).

The area within 2 miles of British Indian Ocean Territory is covered by water (100%), within 10 miles by water (100%), and within 50 miles by water (100%).