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December Weather Forecast

Almost more than any other industry, the weather can predict how busy – or slow – your HVAC work schedule is going to be. Here is the weather forecast for all the major regions where we conduct business. Scroll to find your region.

Southern California (Los Angeles)


Like November before it, December is one of the coolest months in Los Angeles with an average temperature of 14°C (around 56°F). It is also a very wet month with an average of 66 mm of rainfall that falls during the month. The average high temperature still reaches 19°C (about 66°F) but can dip as low as a rather chilly 8°C (around 46°F).

Sunshine Hours

The amount of average daily sunshine drops significantly come December, to about seven hours a day. Your chance of rain on any given day is about 22 percent and the chance of clouds is 15 percent, still giving you an excellent chance of a good day to enjoy the outdoors.


The average number of rainfall days is six, so it would be best to bring a light jacket and an umbrella with the higher chance of showers. You still have a good chance of sunny weather, however, with a 68 percent chance of a sunny day.

Weather in Los Angeles during the winter months is fairly unpredictable and can switch quite rapidly, so it would definitely be best to plan ahead and check the local weather before heading out. And, don’t forget that the temperatures on the coasts are usually 10 degrees colder than the temperatures inland, so plan accordingly when going between the two.

Northern California (San Francisco)


December is winter and the rainy season in San Francisco, USA. This time of year brings gradually falling day time temperatures and an average temperature of 100C. The average high and low temperatures vary from a low of 80C to a day time high of 130C. The highest recorded temperature at this time of year was in 1958 when the temperature reached 240C and the lowest recorded was in 1990 when it only got to -20C. For warmer temperatures and less rain, better months to visit are July and August in the summer season.


This is one of the wettest months of the year with average rainfall at 112mm falling over an average of 10 days in the month. Rain is usually light or moderate but heavier downpours are not uncommon so take an umbrella when you go out. Precipitation varies from year to year depending on the El Nio which brings warmer wetter conditions or cooler, dryer La Nia years that bring less rain. The wettest December on record was in 2002 when 271mm of rain fell in the month and the driest month was in 1989 when only 2mm of rain fell.

The topography of San Francisco means there are several micro-climates with the hills located in the middle of the city affecting the rainfall across the area. The hills protect the suburbs to the east from the colder and wetter extremes of the weather, while neighbourhoods to the west experience generally colder and windier conditions. There is rarely snow during this month but occasional snow flurries may be experienced briefly that do not settle.


Humidity varies from 60% to 90% in this month and tends to get more humid later in the month. Sea temperatures are a chilly 130C so swimming in the bay is only an option for the super brave in this month! Wind speeds are light to moderate at 0 m/s to 6 m/s and tend to decrease later in the month. A 25 day forecast is available for detailed travel planning for the coming weeks.

Arizona (Phoenix)

With an average high-temperature of 66°F (18.9°C) and an average low-temperature of 44.8°F (7.1°C), December is the coldest month in Phoenix. In December, in Phoenix, the average high-temperature is 66°F (18.9°C), and the average low-temperature is 44.8°F (7.1°C). The most humid month is December, with an average relative humidity of 51.8%.

In Phoenix, Arizona, in December, it is raining for 3.9 days, with typically 0.9″ (22.4mm) of accumulated precipitation. In Phoenix, Arizona, the average daily maximum UV index in December is 3.

Idaho (Salt Lake City)

The first month of the winter, December, is also a wintry month in Salt Lake City, Utah, with average temperature fluctuating between 37.9°F (3.3°C) and 22.6°F (-5.2°C).


In Salt Lake City, Utah, the average high-temperature decreases, from a chilly 49.5°F (9.7°C) in November, to a cold 37.9°F (3.3°C). The average low-temperature, in Salt Lake City, is 22.6°F (-5.2°C).


The most humid month in Salt Lake City is December, with an average relative humidity of 74.3%.


In Salt Lake City, it is raining for 9.9 days, with typically 1.4″ (35.8mm) of accumulated precipitation. In Salt Lake City, during the entire year, the rain falls for 95.6 days and collects up to 16.1″ (408.9mm) of precipitation.


Months with snowfall in Salt Lake City are January through May, October through December. The month with the most snowfall in Salt Lake City, Utah, is December when snow falls for 8.2 days and typically aggregates up to 13.2″ (335.3mm) of snow.