The highest day temperature in December 2025 was 101°F. The lowest night temperature was 64°F. The average values for day and night temperatures during December were 91.1°F и 75.1°F respectivly.

Most of the days in December are sunny but you can also expect cloudy and gloomy days.

Precipitation total in December for San Juan is 0.2 in. This value is relatively stable throughout the year.

The average wind speed in December is 10.1 mph. It makes December the most windy month of the year for San Juan.

We are using day length and cloud cover information for each day of the month to calculate averages for this chart. Average sunny hours for San Juan in December is 11.4 hours.