The Proxigean Tide, also called a King Tide, occurs when the Moon is at its closest point in its orbit to the Earth (perigee) and in its New or Full Moon phase as shown in this NOAA SciJinks figure. They also coincide with ‘supermoon’ full moons. At this time, which happens about once every 18 months, the moon’s tidal effect on Earth is maximum. Tidal gravitational forces vary as the third power of the distance between Earth and Moon, so even a small difference in distance can translate into a big effect. The orbit of the moon varies from a distance of 356,500 to 406,700 kilometers with an average distance near 380,000 kilometers. The variation between the maximum and minimum distances results in tidal force changes of a factor of 1.2 times the average tidal forces. The times when this will happen often coincide with major coastal flooding events.
The perigee/apogee and lunar phase calculator at Fourmilab provides a quick means of predicting when these tides will occur. The closest perigee and most distant apogee of the year are marked with “++
” if closer in time to full Moon or “–” if closer to new Moon. Other close-to-maximum apogees and perigees are flagged with a single character, again indicating the nearer phase. Following the flags is the interval between the moment of perigee or apogee and the closest new or full phase; extrema cluster on the shorter intervals, with a smaller bias toward months surrounding the Earth’s perihelion in early January. “F” indicates the perigee or apogee is closer to full Moon, and “N” that new Moon is closer. The sign indicates whether the perigee or apogee is before (“−”) or after (“+”) the indicated phase, followed by the interval in days and hours. Scan for plus signs to find opportunities where the Moon is full close to perigee. The most extreme events based on the time between perigee and Full/New being less than 5 hours:
Date Perigee Phase
3/10/2024 356,893 New
10/17/2024 357,172 Full
4/27/2025 357,118 New
11/5/2025 356,832 Full
6/14/2026 357,195 New
12/24/2026 356,649 Full
8/2/2027 357,361 New
2/10/2028 356,677 Full
9/18/2028 357,047 New
3/30/2029 356,664 Full
11/5/2029 356,899 New
3/17/2030 357,017 Full
12/24/2030 356,924 New
New Moon is pretty bad because both the Sun and the Moon are on the same side of the Earth, and with the Moon near its closest point to the Earth, the tide- making potential is highest. The date for the smallest perigee distance is December 24, 2026 when the Full ‘Super Moon’ will have its largest angular diameter of 2009 arc-seconds or 0.56 degrees.