Though the moon reaches its brightest phase on Thursday night (December 4), its brilliance will be visible from the evening of December 3 through December 5.

The second-largest supermoon of the year

This week, astronomy enthusiasts will witness one of the year’s most captivating spectacles: the December Cold Moon, the second-largest full moon of 2025.

It will rise in the eastern sky at sunset and reach its highest point in the night sky, surpassing the altitude of any other full moon throughout the year.

The Cold Moon will be fully illuminated at 6:14 a.m. (Vietnam time) on December 5 (equivalent to 6:14 p.m. EST on December 4). However, its most mesmerizing appearance will be as it first emerges from the horizon - a moment when the moon appears larger and more dramatic due to an optical illusion known as the “moon illusion.”

The third in a sequence of four supermoons

This Cold Moon marks the third in a rare series of four consecutive supermoons and ranks just behind November’s “Beaver Moon” in apparent size.

A supermoon occurs when a full moon coincides with the Moon's closest approach to Earth in its elliptical orbit, also known as perigee. At this point, the Moon can appear about 10% larger than average.

Though it will be at its fullest at sunset on December 4, the Cold Moon will remain radiant for two nights. On December 5, it will rise approximately an hour after sunset, making early evening skies ideal for stargazers - especially those hoping to test out a new telescope or binoculars during the holiday season.

Why the Cold Moon appears highest in the sky

Each December, the Cold Moon soars higher in the sky than any other full moon of the year. This is due to the Earth's orbit around the Sun. As the winter solstice approaches in the Northern Hemisphere (December 21), the Sun travels its lowest arc across the daytime sky - consequently, the Moon, which always appears opposite the Sun, reaches its highest nighttime arc.

This phenomenon makes the Cold Moon not only bright and large, but also well-positioned for viewing. Observers can clearly see its surface features and lunar geology more distinctly than during other full moons.

The traditional names of the Cold Moon

According to the Old Farmer’s Almanac, Native American tribes across North America gave unique names to December’s full moon based on seasonal and cultural observations. These included names such as “Deer Shed Antlers Moon,” “Popping Trees Moon,” and “Long Night Moon.”

The name “Long Night Moon” is also found in Old English and Anglo-Saxon traditions, referencing the full moon’s proximity to the winter solstice - the longest night of the year.

The next full moon, known as the “Wolf Moon,” will appear on January 3, 2026. It will also be the fourth and final supermoon in this rare lunar sequence.

Hai Phong