California's December Full Moon: What You Need to Know about the Impending Supermoon

A strikingly large moon is set to appear in Californias night sky, marking the final full moon of 2025. This full moon will also qualify as a supermoon, looking unusually bright and expansive to observers in the state. It follows two previous prominent moons: the harvest moon on October 6 and the beaver moon on November 5, creating a rare sequence for stargazers, according to National Geographic.

Timing for Viewing the December Supermoon

The 12th and last full moon of 2025 will reach its peak at 3:14 p.m. on Thursday, December 4, as noted by online calendar Time and Date.

Understanding a Supermoon

A supermoon occurs when a full moon aligns with its closest approach to Earth in its elliptical orbit, called perigee, NASA explains. During this time, the moon can appear up to 14% larger and 30% brighter than when it is at its farthest point, the apogee. At perigee, the moon is approximately 356,000 kilometers from Earth, compared with roughly 406,000 kilometers at apogee.

The Cold Moon Name

Decembers full moon is traditionally called the cold moon, a term from the Old Farmers Almanac. The name stems from the dropping temperatures typical in the last month of the year. Other historical names include the long night moon, drift clearing moon, snow moon, frost exploding trees moon, and hoar frost moon.

European pagans referred to it as the moon before Yule, linking it to the winter solstice celebration, which marks the return of longer daylight hours.

Supermoon Sequence and California Viewing

The December cold supermoon is the third in a series of supermoons in 2025. California ranks among the top 10 states in the U.S. for observing this event, coming in sixth according to the Supermoon Visibility Index by Action Network, which evaluates sky clarity, humidity, elevation, and darkness.

Impact on Nature and Best Viewing Tips

The enlarged winter moon may cause slightly higher tides, known as king tides, along Californias coast, though the effect is modest. The optimal viewing time is near the eastern horizon just after sunset, around 4:45 p.m., when the moon appears especially large due to the moon illusion, a visual effect that makes objects near the horizon seem bigger than those overhead.

Photographers are encouraged to frame the moon against landscapes or structures for dramatic shots. NASA suggests keeping phone flashes off and using tripods to stabilize cameras while focusing directly on the moon.

Next Supermoon in California

The next opportunity to see a supermoon in California will come in early January. The wolf full moon on Saturday, January 3, 2026, will also be a supermoon, creating a four-supermoon streak across the United States.

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• Supermoon to peak soon in California sky. What to know about December’s full moon