December weather forecast
San Juan, PR

December closes the year in San Juan with clear winter signals. Average high temperatures fall to a low of 80.8°F (27.1°C), constituting the perfect recipe for a comfortable holiday season. The sea temperature dips to 81.8°F (27.7°C), and the daylight hours decrease to 11 per day. Consistently, cloud coverage increases to 35%, the highest for the year, offering a cosy shield from the sun. The city's serene ambiance during this month makes it an enticing destination for holiday travellers looking for a temperate getaway.

Temperature

In December, San Juan's weather conditions record an average high-temperature of a still moderately hot 80.8°F (27.1°C), demonstrating little divergence from the preceding month. San Juan in December experiences a minor decline in temperature, with an average low of 75.9°F (24.4°C) at night.

Heat index

For December, the heat index is appraised at a tropical 86°F (30°C). Exhaustion becomes probable with enduring exposure and activity, potentially causing heat cramps.
The heat index's values are generally associated with conditions in shade and light breezes. Exposure to the direct sun could elevate the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'felt air temperature', reflects the feeling of heat when considering both air temperature and humidity. Factors such as metabolic variation, pregnancy, and physical activity play a role in one's impression of weather. Consider the sun's direct rays and their impact; they can potentially increase the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are largely significant for babies and toddlers. Children often overlook the necessity for resting and fluid replenishment. Thirst is a late sign of dehydration - thus, it is critical to stay hydrated, especially during extended periods of physical activities.

Humidity

The average relative humidity in December in San Juan is 77%.

Rainfall

In San Juan, in December, during 14.5 rainfall days, 0.98" (25mm) of precipitation is typically accumulated. Throughout the year, there are 159.9 rainfall days, and 12.01" (305mm) of precipitation is accumulated.

Ocean temperature

In San Juan, the average seawater temperature in December is 81.9°F (27.7°C).
Note: Swimming, diving, and other activities in water temperatures between 77°F (25°C) and 84.2°F (29°C) are thought to be quite enjoyable and satisfying for extended periods, with no discomfort.

Daylight

With an average of 11h and 0min of daylight, December has the shortest days of the year in San Juan.
On the first day of December, sunrise is at 6:40 am and sunset at 5:46 pm. On the last day of the month, sunrise is at 6:56 am and sunset at 5:59 pm AST.

Sunshine

The month with the least sunshine is December, with an average of 6.6h of sunshine.

UV index

The months with the lowest UV index 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 exposure to the Sun's UV rays for the average person.
Note: A maximum UV index of 6 in December translates into the following recommendations:
Steer clear of overexposure. Fair-skinned individuals can be scorched in less than 20 minutes. Be aware that the sun's UV radiation is strongest between 10 a.m. and 4 p.m. and try to reduce direct sun exposure during this period as much as possible. For excellent sun protection for the eyes, ears, face, and neck, consider a wide-brim hat. Caution! Sand and water surfaces escalate the UV intensity from the Sun.