This month's full moon, known as the "cold moon," is on a rare 18.6 year cycle and will visible on Sunday.
It's a busy weekend in the night sky. Not only do sky gazers have a chance to see the year's most colorful meteor shower, but it's also the last and longest full moon of the year, and one that won't be seen again until 2043.
Known as the "cold moon" -- due to the long, cold nights typical of December -- the full moon that appears this weekend, just ahead of the Dec. 21 winter solstice, is an oddity. In fact, there are three particularly rare things about this month's cold moon, sometimes also called the "frost moon" or "winter moon":
Rising and setting at its most northern points
The moon, like the sun, rises and sets in approximately the eastern and western skies. The key word is "approximately." Because the Earth's axis is tilted, neither the moon nor the sun rise or set directly to the east or west.
The exact positions of moonrise and moonset are dictated by the time of year and the phase of the moon. The full moon rises and sets at its most northern points on the horizon in December, when the Earth's North Pole is tilted the farthest away from the sun.
The most northern position until 2043
There's something extra special about this year's cold moon. It will rise and set not just at its most northern points of the year, but of any point in nearly two decades. This is because, as timeanddate.com explains, "the moon's tilted orbit slowly gyrates, in a similar way to a gently wobbling gyroscope or spinning top."
This phenomenon, called the "lunar precession," occurs on a cycle that repeats every 18.6 years. This month's full moon will coincide with an approximately two-year period of the cycle, known as "major lunar standstill," when the most extreme moonrise and moonset positions are even more extreme due to the moon's wobble.
After this weekend, the moonrise and moonset won't occur this far north on the horizon until 2043.
It could affect your meteor shower viewing
Ironically, one celestial rarity could interfere with viewing another. The light from this weekend's full moon could make it hard to see shooting stars from the Geminid meteor shower.
The Geminids are considered "one of the best and most reliable annual meteor showers," according to NASA. This year's display is expected to peak Friday night, but there should still be shooting stars on Saturday night.
When and where to look at the cold moon
This weekend's full moon officially occurs Sunday at 4:02 a.m. Eastern time. That's when the moon will pass opposite the sun. There will, however, be plenty of hours before and after that time to look up and see the moon, assuming it's not too cloudy in your location.
For example:
In D.C., the moon rises Saturday at 3:53 p.m. local time in the northeast sky and sets Sunday at 7:54 a.m. in the northwest sky.In Chicago, the moon rises Saturday at 3:24 p.m. local time in the northeast sky and sets at 7:51 a.m. in the northwest sky.In Los Angeles, the moon rises Saturday at 4:02 p.m. local time in the northeast sky and sets Sunday at 7:28 a.m. in the northwest sky.