The highest day temperature in December 2025 was 91°F. The lowest night temperature was 44°F. The average values for day and night temperatures during December were 76.0°F и 51.5°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 Bernardino is 0.8 in. It makes december one of the most rainy months of the year.

The average wind speed in December is 3.6 mph. This value is relatively stable throughout the year.

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 Bernardino in December is 7.3 hours.