The December full moon is called the Long Night’s Full Moon because midwinter nights are at their longest and darkest and the full moon is seen above the horizon for a long time. The midwinter full moon has a high trajectory across the sky because at this time the sun is low in the sky.
December full moon is also known as the Full Moon before Yule, thus I have illustrated this moon with a huge bonfire on a Yule log. And this moon is also known as the Full Cold Moon, too.
On Sunday, December 3, 2017, this full moon is also the year’s one and only full supermoon. This December moon comes close enough to Earth (222,443 miles or 357,987 km) to enjoy supermoon status. This makes the full moon look extra close and extra bright.