Guide

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Why the winter full moon rides so high in the sky

December to January

The full moons of December and January climb high in the south around midnight and stay up through most of the long night, the reverse of the low summer full moon. A full moon sits opposite the sun, so when the sun's path is at its lowest, the full moon's path is near its highest.

Why this time of year

In Massachusetts this month's full moon crosses due south around midnight about 62 to 76 degrees up, depending on the year, compared with about 18 to 29 degrees for a June full moon. It is above the horizon for about 14 to 16 and a half hours, against about 8 and a half to 10 in June. (Calculated from US Naval Observatory data for every full moon from 2019 to 2037.)

How to notice it

  1. On the night of the full moon, find it around 9 pm. It is in the east to east-southeast, already higher than the sun was at lunchtime that day.
  2. Look again near midnight, when it crosses due south at its highest: roughly two-thirds to five-sixths of the way from the horizon to straight overhead.
  3. Notice that it rose in the northeast to east-northeast around sunset and sets low in the west-northwest to northwest around dawn.
  4. Think back to a June full moon, which skims low over the southern trees and is up only about 8 to 10 hours. Same moon, opposite path.

Try this with kids: Around 9 o'clock on full moon night, point to where the sun was at lunch, then point to the moon. Which one is higher?

Word to know: “Altitude”: how many degrees above the horizon something is, with 90 degrees straight overhead.

Sources

  • earthsky.orgSecondary (EarthSky, posted 2025-12-03 by the Editors of EarthSky and John Jardine Goss, a dated article, not a rolling page). The mechanism: 'Every full moon is more or less opposite the sun.' 'The high arc across the sky of the December full moon closely matches that of the June sun.' It also links the longest night to the full moon staying up all night ('the December full moon is called the Long Night Moon'). Its wording 'rise to nearly the top of the sky' is NOT used in the card: at this latitude the calculated peak is 62 to 76 degrees. ROLLING RISK (landmine 30): the slug is evergreen but the post is refreshed each December with that year's dates and title (read 2026-11-06 showing the December 2025 edition). The mechanism is carried without it by the USNO calculations and the Griffith page.
  • griffithobservatory.lacity.govPrimary institutional (Griffith Observatory). The year-to-year effect: 'Every 18.6 years, our Moon reaches the extremes of its orbit around the Earth.' At a major standstill the moon can be seen 'rising higher in the sky than the summer solstice Sun or lower in the sky than the winter solstice Sun.' The previous one was 'in January 2006'; the page covers the 2024-2025 standstill.
  • science.nasa.govPrimary (NASA APOD, 2025-06-20; apod.nasa.gov/apod/ap250620.html redirects here). Major lunar standstills are 'driven by the 18.6 year precession period of the lunar orbit.' This backs the 18.6-year cycle only, not heights.
  • aa.usno.navy.milPrimary data (USNO). Full moon instants in UT: 2026-06-29 23:56, 2026-12-24 01:28, 2027-01-22 12:17, 2027-02-20 23:23. The 2019-2037 full-moon list for the multi-year calculation came from the same API's year endpoint (aa.usno.navy.mil/api/moon/phases/year?year=YYYY), queried by script.
  • aa.usno.navy.milPrimary data (USNO), 42.4 N 71.3 W, EST. December 2026 full moon night: moonrise 15:40 Dec 23, upper transit 23:54, set 08:03 Dec 24 (the Dec 24 query), so it is up 16 h 23 min. Sun Dec 23: set 16:17, rise Dec 24 07:13. The other rise, transit and set times in the table came from the same API with other dates.
  • aa.usno.navy.milPrimary data (USNO celestial navigation API, UT input). At the December 2026 full moon's transit (23:54 EST): Moon computed altitude 74.72 degrees, declination +27.12, azimuth 179.9. Topocentric altitude about 74.45 after subtracting the API's parallax-in-altitude 0.27. The same API, at other times, gave every altitude in this report, including the winter-solstice noon sun at 24.16 degrees (2026-12-21 16:43 UT) and the summer-solstice noon sun at 71.03 degrees (2026-06-21 16:49 UT).

Checked against these sources on November 6, 2026.

In the guide for December, January

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