December weather forecast
Yellowstone National Park, WY

December invites the harshest cold of the year, after January, to Yellowstone National Park. An arctic climate prevails, drawing a curtain of frost across the landscape. A substantial snowfall of 30.5" (775mm) blankets the park, creating a crisp, white scenery. Short daylight and sunshine hours give December its icily tranquil ambiance. Bison puffing visible clouds of breath become a mesmerizing sight against the frost-laden backdrop.

Temperature

The coldest temperatures occur during December, when averages reach a peak of 24.3°F (-4.3°C) and a low of 5°F (-15°C).

Rainfall

In Yellowstone National Park, in December, during 15.6 rainfall days, 1.61" (41mm) of precipitation is typically accumulated. In Yellowstone National Park, during the entire year, the rain falls for 151 days and collects up to 20.91" (531mm) of precipitation.

Snowfall

Months with snowfall in Yellowstone National Park are January through June, September through December. In Yellowstone National Park, during December, snow falls for 14.9 days and regularly aggregates up to 30.51" (775mm) of snow. In Yellowstone National Park, during the entire year, snow falls for 91.4 days and aggregates up to 193.7" (4920mm) of snow.

Daylight

December has the shortest days of the year, with an average of 8h and 54min of daylight.
On the first day of December, sunrise is at 7:39 am and sunset at 4:44 pm. On the last day of the month, sunrise is at 7:58 am and sunset at 4:52 pm MST.

Sunshine

The month with the least sunshine is December, with an average of 4h of sunshine.

UV index

January and December, with an average maximum UV index of 1, are months with the lowest UV index. A UV Index estimate of 2, and below, represents a minimal health hazard from exposure to the Sun's UV radiation for the ordinary person.
Note: The UV index of 1 during December translates into the following guidance:
Prolonged sun exposure should always be prevented in babies, children, and those with sensitive skin. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Your best bet for sun defense on the face, eyes, and neck is a hat with a wide brim. Consider this! The reflection from snow can almost double the intensity of the Sun's UV radiation.