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

December tends to be the coldest month, with temperatures averaging a daily high of 24.3°F (-4.3°C) and a low of 5°F (-15°C).

Rainfall

In December, the rain falls for 15.6 days. Throughout December, 1.61" (41mm) of precipitation is 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

January through June, September through December are months with snowfall in Yellowstone National Park, Wyoming. In Yellowstone National Park, in December, snow falls for 14.9 days, with typically accumulated 30.51" (775mm) of snow. Throughout the year, there are 91.4 snowfall days, and 193.7" (4920mm) of snow is accumulated.

Daylight

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

Sunshine

December has the least sunshine of the year, 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 value of 2, and less, symbolizes a low threat to health from exposure to the Sun's UV rays for the average person.
Note: In December, the average maximum UV index of 1 translates into the following recommendations:
Unlike children, who always need sun protection, most individuals can remain in the sun for up to an hour without getting burnt. Limiting sun exposure during midday hours helps in reducing the harmful effects of UV radiation. For optimum UV protection, wear sun-resistant attire complemented with a hat and quality shades. On your guard! Snow's reflection can almost double the intensity of the Sun's UV radiation.