The full cold moon peaks this weekend – offering a lunar phenomenon that happens once every 18.6 years

The last full moon of 2024, the cold moon, will light up the night sky on Sunday, December 15. The moon will rise and set at its most extreme northern points on the horizon, the result of a once-every-18.6-year phenomenon known as a major lunar phase, according to TimeandDate.com.

What is a major moon phase?

A major lunar standstill occurs when the moon reaches the extremes of its orbit around Earth, the Griffith Observatory said in a declaration. The moon reaches both a northernmost and a southernmost position every 29 days, but from month to month the northern and southern limits of moonrise and moonset change. “During an 18.6-year cycle, the greatest north and south positions of the moon extend beyond that of the sun,” the observatory said. “And just as the sun dwells at its limits at each solstice, as soon as the moon reaches these extremes, its limits do not seem to change.”

While the sun stands still for just a few days, a major lunar standstill can last for two years. During this time, we observe the moon rise and set in its northernmost and southernmost positions on the horizon, the Observatory said.

Why is it called the cold moon?

December’s full moon is referred to as the cold moon, which is “a Mohawk name that conveys the cold conditions at this time of year when cold weather really begins to grip us,” Old farmer’s almanac says.

It is also known as the long night moon because it is the closest full moon to the winter solstice, which is the longest night of the year, according to NASA. This year, the winter solstice occurs a few days after the full moon on Saturday, December 21.

How to see the full cold moon

According to NASA, the cold moon will occur on Sunday 15 December and will pass opposite the sun at 4:02 AM EST. While the moon will officially be full on Sunday, it will also appear full on Saturday, December 14 and Monday, December 16.