December weather forecast
Ascension Island, Saint Helena, Ascension and Tristan da Cunha

The first month of the summer, December, is still a warm month in Ascension Island, Saint Helena, Ascension and Tristan da Cunha, with temperature in the range of an average low of 22°C (71.6°F) and an average high of 29°C (84.2°F).
The perfect water temperature of 25°C (77°F) with 4mm (0.16") of accumulated rainfall and only 1 rainfall days, makes December a great period for swimming and other water activities.

Temperature

In Ascension Island, the average high-temperature in December is almost the same as in November - a still warm 29°C (84.2°F). In Ascension Island, the average low-temperature is 22°C (71.6°F).

Heat index

In December, the average heat index is appraised at a hot 32.5°C (90.5°F). Take special precautions - heat exhaustion and heat cramps are expected. Heatstroke may occur with lengthy activity.
Note that heat index values are valued for light wind and location in the shade. Exposure to direct sunshine can increase heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like', 'apparent temperature', 'real feel', or 'felt air temperature', is calculated by taking the relative humidity value for a specific location and factoring it into the air temperature reading. This effect is subjective, depending on the activity and individual's heat perception influenced by various reasons (wind, metabolic differences, clothing). Be aware that direct exposure to sunlight increases heat impact and may raise the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.

Humidity

In Ascension Island, the average relative humidity in December is 69%.

Rainfall

The months with the least rainfall in Ascension Island are January, November and December Rain falls for 1 days and accumulates 4mm (0.16") of rain.

Sea temperature

In Ascension Island, Saint Helena, Ascension and Tristan da Cunha, the average seawater temperature in December is 25°C (77°F).
Note: For swimming, diving, and other water activities, temperatures between 25°C (77°F) and 29°C (84.2°F) are perceived as very enjoyable and pleasurable for prolonged periods without feeling uncomfortable.

Daylight

With an average of 12h and 35min of daylight, December has the longest days of the year.
On the first day of December, sunrise is at 06:29 and sunset at 19:03. On the last day of the month, sunrise is at 06:43 and sunset at 19:17 GMT.

Sunshine

The average sunshine in December in Ascension Island is 6.4h.

UV index

The months with the highest UV index are January through April, September through December, with an average maximum UV index of 12. A UV Index reading of 11, and higher, represents an extreme health hazard from unprotected exposure to Sun's UV rays for ordinary individuals.
Note: The average daily UV index of 12 in December transform into the following instructions:
Practice all essential precautions. Protection against sun damage is crucial. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. Even on cloudy days, a sunscreen with a minimum 30 sun protection factor should be generously applied and frequently re-applied, including after every swim or outdoor exercise. Beware! The reflection of water and sand dramatically increases exposure to the UV rays.