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

San Juan starts December with an average high-temperature of a still moderately hot 80.8°F (27.1°C), hinting at a minimal fluctuation from November. San Juan experiences an average nighttime temperature of 75.9°F (24.4°C) in December, reflecting a minor difference from the day's peak.

Heat index

In December, the heat index is estimated at a hot 86°F (30°C). If one continues to be active during exposure, it might cause tiredness and subsequent heat cramps.
Heat index specifics point out values are for conditions of shade and a slight breeze. With exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'real feel' or 'felt air temperature', joins air temperature with relative humidity to produce a temperature perception for humans. The influence of weather can be personal, changing with an individual's body mass, height, and level of physical exertion. Being under direct sunshine can magnify the heat experience, possibly pushing up the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are extremely vital to babies and toddlers. Young ones often ignore the need to take a break and drink fluids. Thirst is a late-stage symptom of dehydration - hence, maintaining hydration, particularly during extended physical activities, is crucial.

Humidity

The average relative humidity in December is 77%.

Rainfall

In San Juan, in December, 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 December, the average ocean temperature is 81.9°F (27.7°C).
Note: Surface water temperatures falling between 77°F (25°C) and 84.2°F (29°C) are regarded as prime and extremely agreeable for enduring periods during any water activity.

Daylight

With an average of 11h and 0min of daylight, December has the shortest days of the year.
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

December has the least sunshine of the year, 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 estimate of 6 to 7 represents a high health hazard from exposure to the Sun's UV radiation for the average person.
Note: During December, 6 as the daily maximum UV index converts into the following advice:
Conform to measures and uphold sun safety traditions. Warding off skin and eye harm is necessary. Between 10 a.m. and 4 p.m., UV radiation is strongest. Make an effort to avoid direct sunlight during this time, remembering that shade structures may not provide full sun protection. Employ a hat with a wide brim for robust protection, cutting UV exposure by half. Stay vigilant! UV rays get a boost in intensity due to sand and water reflections.