United States - weather in December

December is the first month of winter in the United States, and it is the coldest of the year in the westernmost part (see Seattle, Los Angeles, Denver, Phoenix), while in the rest of the territory, the coldest month is February.
The average temperatures vary a lot: they are above freezing on the west coast, facing the Pacific, quite mild even in the northern part (see Seattle), and very mild in the south (see Los Angeles), where they are spring-like. In the south, the average is above freezing as well, and in the southern tip of Florida (see Miami), the December average is about 22 °C (71.5 °F) and the climate is tropical.
Instead, in inland areas, December is a cold month, very cold in the north, with averages below freezing, and cold in the central band, with averages just above freezing (see Kansas City) also on the Atlantic coast (see New York). The Great Lakes, on the border with Canada, begin to freeze, generally from the end of the month, more or less extensively depending on the temperature.
Furthermore, cold waves can occur in almost the entire territory, which can significantly lower the temperature. In general, only the coast of California (see San Francisco, Los Angeles) and southern Florida (see Miami) are sheltered from cold spells. In the Great Plains the blizzard, the icy north wind, can blow, while in the Great Lakes and in the north-east, in New England (see Boston, Portland in Maine), and sometimes also in New York and Washington, there can be snowstorms, especially in the second half of the month.
In the Rocky Mountains, there are several resorts where you can practice winter sports.
On the eastern side of the mountains (see Helena, Denver), the chinook can blow, a mild, dry wind capable of melting snow.
Precipitation is abundant on the northwest coast, in the states of Washington and Oregon (see Seattle), but also in northern California. On the central-southern coast of California (see San Francisco, Los Angeles), the rains are gradually rarer, however, winter is the rainiest season and there can be waves of bad weather.
In the Great Basin, the arid western plateau, precipitation is quite scarce, however, it can occur in the form of snow. In the Great Plains (see Fargo), east of the Great Basin, light snowfalls generally occur as well. In the deserts of the southwest (see Las Vegas, Phoenix), the rains are rare.
Instead, in the central-eastern part of the United States, precipitation is more frequent and abundant, and in the northern part, on the Great Lakes and in New England, it often occurs in the form of snow.
The United States is located at medium latitudes, however, the days are quite short in the north, where the sun stays above the horizon for less than 9 hours on average. December 21 is the winter solstice in the Northern Hemisphere, which is to say, the day with the least hours of daylight of the whole year.

The sea is warm enough for swimming only in the southeastern part of Florida, from Miami to Palm Bay.


See also: United States, the weather in November - January
The climate of United States