December weather forecast and climate
San Juan, PR

An old fort building and a view of the stunning San Juan city, Puerto Rico
An old fort building and a view of the stunning San Juan city, Puerto Rico

Weather in December

The first month of the winter, December, is also a moderately hot month in San Juan, Puerto Rico, with average temperature fluctuating between 80.8°F (27.1°C) and 75.9°F (24.4°C).

Temperature

In December, the average high-temperature is relatively the same as in November - a still moderately hot 80.8°F (27.1°C). The average low-temperature, is 75.9°F (24.4°C).

Heat index

In December, the average heat index is appraised at 85.5°F (29.7°C). Constant exposure and activity lead to possible fatigue. Prolonged exercise may result in heat cramps.
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 'apparent temperature', 'feels like', '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, pregnancy, clothing). Be aware that direct exposure to sunlight increases heat impact, and may raise the heat index additionally, 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

The average relative humidity in December is 77%.

Rainfall

In San Juan, it is raining for 14.5 days, with typically 0.98" (25mm) of accumulated precipitation. In San Juan, during the entire year, the rain falls for 159.9 days and collects up to 12.01" (305mm) of precipitation.

Ocean temperature

In San Juan, the average seawater temperature in December is 81.9°F (27.7°C).
Note: For any water activity, surface water temperatures between 77°F (25°C) and 84.2°F (29°C) are considered as excellent and extremely pleasant for lengthened periods.

Daylight

December has the shortest days of the year, with an average of 11h of daylight.

Sunshine

December has the least sunshine of the year in San Juan, with an average of 6.6h of sunshine.

UV index

Months with the lowest UV index in San Juan are January through March and December, with an average maximum UV index of 6. A UV Index of 6 to 7 symbolizes a high threat to health from the exposure to the Sun's UV rays for ordinary individuals.
Note: The average daily UV index of 6 transform into the following instructions:
Take precautions and adopt sun safety practices. Protection against sunburn is obliged. 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. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun. Beware! The strength of the UV rays is significantly increased by the reflection of the water and sand.
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FAQ

What is the temperature in December in San Juan?

In December, in San Juan, Puerto Rico, the average high-temperature is 80.8°F (27.1°C), and the average low-temperature is 75.9°F (24.4°C). In December, the average heat index (a.k.a. 'real feel', 'felt air temperature'), that calculates temperature value influenced by the moisture in the air, is estimated at 85.5°F (29.7°C).

What is the average humidity in December in San Juan?

In December, the average relative humidity in San Juan is 77%.

How much does it rain in San Juan in December?

In San Juan, during December, the rain falls for 14.5 days and regularly aggregates up to 0.98" (25mm) of precipitation.

What is the ocean temperature in December in San Juan?

In San Juan, the average seawater temperature in December is 81.9°F (27.7°C). For swimming, diving, and other water activities, temperatures between 77°F (25°C) and 84.2°F (29°C) are perceived as very enjoyable and pleasurable for prolonged periods without feeling uncomfortable.

What is the month with the shortest days in San Juan?

The month with the shortest days in San Juan, Puerto Rico, is December, with an average of 11h of daylight.

What is the average length of the day in December in San Juan?

The average length of the day in December is 11h.

What is the month with the least sunshine in San Juan?

The month with the least sunshine in San Juan, Puerto Rico, is December, with an average of 6.6h of sunshine.

How long on average sun shines in December in San Juan?

In December, the average sunshine in San Juan is 6.6h.

When is the lowest UV index in San Juan?

Months with the lowest UV index are January through March and December, with an average maximum UV index of 6.

What is the UV index intensity in December in San Juan?

In December, the average daily maximum UV index in San Juan is 6. A UV Index of 6 to 7 symbolizes a high hazard to health from the exposure to the Sun's UV rays.

Average temperature in December
San Juan, PR

Average temperature in December - San Juan, PR
  • Average high temperature in December: 80.8°F

The warmest month (with the highest average high temperature) is August (85.1°F).
Months with the lowest average high temperature are January and March (79.9°F).

  • Average low temperature in December: 75.9°F

Months with the highest average low temperature are August, September and October (79.2°F).
The coldest month (with the lowest average low temperature) is March (73.9°F).

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Average pressure in December
San Juan, PR

Average pressure in December - San Juan, PR
  • Average pressure in December: 29.98"

Months with the highest atmospheric pressure are January and February (30.02").
The month with the lowest atmospheric pressure is October (29.9").

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Average wind speed in December
San Juan, PR

Average wind speed in December - San Juan, PR
  • Average wind speed in December: 9.9mph

The windiest month (with the highest average wind speed) is July (10.7mph).
The calmest month (with the lowest average wind speed) is October (7.4mph).

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Average humidity in December
San Juan, PR

Average humidity in December - San Juan, PR
  • Average humidity in December: 77%

Months with the highest relative humidity are May, June and July (79%).
Months with the lowest relative humidity are February and March (76%).

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Average rainfall in December
San Juan, PR

Average rainfall in December - San Juan, PR
  • Average rainfall in December: 0.98"

The wettest month (with the highest rainfall) is November (1.57").
The driest month (with the least rainfall) is April (0.55").

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Average rainfall days in December
San Juan, PR

Average rainfall days in December - San Juan, PR
  • Average rainfall days in December: 14.5 days

The month with the highest number of rainy days is November (16.1 days).
The month with the least rainy days is June (10.3 days).

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Average sea temperature in December
San Juan, PR

Average sea temperature in December - San Juan, PR
  • Average sea temperature in December: 81.8°F

The best month for swimming (with the highest average sea temperature) is September (84.9°F).
The coldest month (with the lowest average sea temperature) is February (78.9°F).

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Average daylight in December /
Average sunshine in December
San Juan, PR

Average daylight in December / Average sunshine in December - San Juan, PR
  • Average daylight in December: 11h

The month with the longest days is June (Average daylight: 13.2h).
The month with the shortest days is December (Average daylight: 11h).

  • Average sunshine in December: 6.6h

The month with the most sunshine is June (Average sunshine: 10.9h).
The month with the least sunshine is December (Average sunshine: 6.6h).

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Average sunshine days in December
San Juan, PR

Average sunshine days in December - San Juan, PR
  • Average sunshine days in December: 9.5 days

The month with the most sunshine days is June (13.7 days).
The month with the least sunshine days is November (9.4 days).

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Average UV index in December
San Juan, PR

Average UV index in December - San Juan, PR
  • Average UV index in December: 6

Months with the highest UV index are April, May, June, July, August, September, October and November (UV index 7).
Months with the lowest UV index are January, February, March and December (UV index 6).

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Average cloud cover in December
San Juan, PR

Average cloud cover in December - San Juan, PR
  • Average cloud cover in December: 35

The month with the most cloud cover is December (Cloud cover 35).
The month with the least cloud cover is September (Cloud cover 26).

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Average visibility in December
San Juan, PR

Average visibility in December - San Juan, PR
  • Average visibility in December: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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