What is tonight’s supermoon?
On the evening of December 4, the full Cold Moon reaches peak illumination while it is near perigee, making it qualify as a supermoon. Astronomers often describe this as a perigean full moon, where the Moon is closer than average and appears slightly larger and brighter in the sky.
- See latest full moons in the past year
How much bigger and brighter is it?
Even though social media hype can make it sound dramatic, the size difference is modest. A perigee full moon is on the order of up to about 14 percent larger in diameter and roughly 30 percent brighter than a full moon at apogee, but most casual observers only notice that it looks extra crisp and bright on a clear night. The strong “wow” factor usually comes just after moonrise, when the Moon is low on the horizon and the well-known moon illusion makes it look oversized compared to trees, homes, and city skylines.
Is this really the last supermoon of the year?
For 2025, yes—December 4 is the final full moon and the final supermoon on the calendar. This Cold Moon follows supermoons earlier in the season, and the next supermoon does not arrive until early 2026. The reason “last supermoon of the year” sounds repetitive is that a typical year includes three or four supermoons, and each one tends to get promoted as a big, final chance to look up, even though the pattern repeats most years.
Why is it called the Cold Moon?
The December full moon is traditionally known as the Cold Moon, a name tied to the onset of winter and the longer, colder nights in the Northern Hemisphere. Some traditions also refer to it by alternative names like the Long Night Moon or Oak Moon, all nodding to the season’s darker, colder stretch of the year.
When and how to watch (weather angle)
The December 4 supermoon reaches its fullest phase around the late evening in North America, but it will look essentially full from December 3–5, offering multiple nights to dodge clouds. For the most dramatic view, plan to step outside around local moonrise and face the eastern horizon, where thin high clouds can add a halo but thicker overcast will wash out the show.
November Supermoon Closest to Earth Since 1948
On November 14th, our closest celestial neighbor will reach its full phase as it orbits behind the Earth where the sun, Earth, and moon are aligned, respectively. As the lunar orbit reaches its closest approach to Earth, it is called a perigee. The moon’s orbit is elliptical around the Earth and as a result, the proximity of distance between the moon from the Earth varies during each orbital cycle (as do all planetary bodies and their respective satellites in the solar system, but that is not including comets, meteors, etc., that have different orbital patterns otherwise known as orbital eccentricity).
When the moon reaches its closest point to Earth in orbit, it is dubbed the name of a supermoon. The proper nomenclature for the supermoon in the full or new moon phase is called the perigee-syzygy, where the sun, Earth, and moon, are aligned when the moon is in its closest orbital approach around the Earth during the new and/or full moon phase.
The opposite of the perigee is the apogee, for when the moon reaches its furthest point from Earth (otherwise known as a micromoon, or apogee-syzygy). Apogee and perigee periods occur approximately once a month, as a lunar cycle is roughly 27.3 days. A complete phase cycle of the moon is about 29.5 days from new moon-to-new moon phase.
While there is no synchronicity between perigee and apogee periods with respect to the moon’s phase, it just so happens that on November 14th, the moon will be in its full phase while in perigee. The moon will look much larger than usual, and much brighter as the sunlight reflects off of the lunar surface. Thus, astronomers are predicting that the moon will have a lunar illumination ~30% brighter than during a usual full moon phase.
This is the second full moon phase to encounter a perigee-syzygy of 2016, of which the previous supermoon that was in its full phase occurred last month on October 16th. The next time the moon will be even closer to Earth while in its full phase compared to what will occur on November 14th will be in 2034.