What is a Supermoon? Everything You Need To Know

There's a lot of talk of "Supermoons" these days. But what are they, and how are they different from a regular full Moon? We explain.

There will be four Supermoons in 2022. The first was on May 16 (which also happened to be a total eclipse of the Moon). The second was on June 14. The third will be the Full Buck Moon on July 13, 2002. The fourth Supermoon of the year will be the Full Sturgeon Moon on August 11.

July’s Supermoon will be the largest of 2022 because the Moon will also be at perigee. Perigee is the astronomical term for when the Moon comes closest to Earth in its orbit. While July’s full Moon may be the largest, the Moon may not appear to be any bigger or brighter than the other Supermoons. Learn about the “Moon Illusion.”

However, beware! The Supermoon on July 13 may cause coastal flooding. Tides will be noticeably higher due to the combined gravitational forces of the Sun/Earth/Moon alignment. Places that are located near and along ocean shorelines will be most prone to flooding, especially along the Atlantic Seaboard where a coastal storm or tropical cyclone may aggravate the situation by producing higher-than-normal tides on top of the already higher-than-normal water levels.

Tidal heights vary from one coastal location to another, depending on the topography. Historically, the “Saxby Gale” of 1869 is often referenced when unusually high tides coincide with a potent storm.  (Read more about the Saxy Gale.)

What Is A Supermoon?

Supermoons are caused by the shape of the Moon’s orbit, which is not a perfect circle. The Moon orbits in an ellipse, or oval, shape. Each month, it reaches a point farthest from the Earth, called apogee, and a point closest to the Earth, called perigee.

A Supermoon occurs when the Moon is at least 90% of the way to its perigee position at the same time it is in its “full” or “new” phase. An extreme perigean Supermoon is when a full or new Moon happens at the same time the Moon is at perigee.

See all the upcoming full Moon dates.

Why New And Full Phases?

The reason these two Moon phases are singled out is because each of them means that the Sun, Earth, and Moon are in alignment. When the Moon is full, it sits exactly on the opposite side of the Earth from the Sun. When the Moon is new, it sits between the Earth and the Sun. In both cases, the gravitational pull from these two bodies—the Moon and the Sun—combine to create higher-than-normal tides, called “spring tides,” on Earth. When the Moon is also at perigee at this time, the effect is magnified into what is called a “proxigean spring tide.”

Of course, a new Moon at perigee isn’t very exciting to look at because in the new phase, the Moon does not reflect the Sun’s light, so it is invisible to the naked eye. So, understandably, full Supermoons get all the attention.

What’s In A Name?

We’ve heard from many of our readers on social media that they’re tired of hearing the term “Supermoon” so often. “It seems like every full Moon is a Supermoon!” The term became popular in March 2011 when the Moon’s perigee brought it to 221,565 miles of Earth; within 127 miles of the absolute closest that it can come (the absolute closest the Moon can come is 221,438 miles from Earth; an exceedingly rare occurrence).

In actuality, Supermoons should only be applied to “extreme” perigees, in which the full Moon approaches a distance of 221,472 miles or less. Between the years A.D. 1500 to 2500, this condition is met only 14 times, or on average once about every 71 years. The last time the full Moon came this close to Earth was January 15, 1930 (221,454 miles) and the next time will be on December 6, 2052 (221,469 miles).

But if you follow the 90% rule noted above, you can have as many as three—and on some occasions even four or five—Supermoons in a single year! Here at Farmers’ Almanac, however, we don’t like to “water down” the term and believe that a full Moon is truly a Supermoon when the full phase coincides (or very nearly so) with its closest perigee for a given year. Which happens once. However, we realize that many do enjoy the “Supermoon” terminology and want to celebrate Supermoons more often, so we usually bring attention to two of the closest Moons in the year.

Not All Supermoons Are Created Equal!

Just as the Moon’s orbit isn’t a perfect circle, it also varies slightly from month to month and year to year. Its perigee during one month may be slightly farther from the Earth than its perigee the next month. 

Many people speculating that extreme Supermoons can cause natural disasters such as earthquakes, volcanoes, and tsunamis. But most astronomers dismiss this line of thinking, though, arguing that the 2,000-mile difference — less than 1% of the Moon’s total distance from the Earth — is minimal in the grand scheme of things and unlikely to cause much disruption on Earth, beyond the usual perigean spring tide.

Regardless of what you believe about a Supermoon’s impact on Earth, or what you call it, one thing is certain: if the sky is clear, the view of the rising Moon will always be amazing, so get outside and enjoy it!

Learn about July’s Night Sky.

This article was published by the staff at Farmers' Almanac. Do you have a question or an idea for an article? Contact us!

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youjizz

The supermoon may look especially large to you, however, if it’s very close to the horizon. But that has nothing to do with astronomy and everything to do with how the human brain works. This effect is called the “moon illusion” and may arise from at least a couple of different things. Scientists suggest that perhaps the brain is comparing the moon to nearby buildings or objects, or perhaps our brain is just wired to process things on the horizon as bigger than things in the sky.

nicole holcomb

I haven’t seen any thing kind of like that here in alabama lmao 🙂

jenny

I saw it okay last night in Australia. Very bright, couldn’t see any significant difference in size.

Kim

Awesome Moon,which I enjoy.It appeared brighter,not bigger,here in Maine.I saw it & took pics,which I posted.Thanks,I follow the Moons dates,names,& meanings!

jenny

Will we get the same effect here on the other side of the Earth? I’ll certainly be looking out for it anyway. Thanks for that info.

ray crannell

guess i miss supermoons in the pass i’ll see this one i hope!
does it have effect on the weather?

Jaime McLeod

Ray, That’s controversial, but most meterologists say “no.” It will have an effect on the tides, though, making them higher than normal.

Donna

We have an “AWESOME” God and he sends us beautiful presents to enjoy. Hope we can see the moon in Indiana…waiting.

Angie

In 2011 God was tolerating us. 2019-2020…let’s just say it’s time we get some punishment for our bad behavior. God is some kind of pissed off at the moment

Mr.Bill

very kool just what i needed to brighten up this long cold winter thanks.

Angie

If you only knew then what you know now lol. Who would of EVER thought the entire world would be hiding from or quarantined from the COVID-19 global pandemic. I’ll see it on Tuesday, from the safety of a wide open field

The Occupant

Everyday there are awesome wonders of God. Some days are more AWESOMER 🙂

Andrew Grasso

Thanks for posting this article for me Jaime!

Beverly De Fronzo

Wow! What an awesome Birthday present I cannot wait to see it! Hope the weather cooperates!

midnghtldy

Would love to be sitting on a beach in Hawaii gazing at a moon similar to the one in the above photo. Also I agree with Willow, that Our God does give us some very amazing sites to enjoy.

Richard

This is very interesting and if the weather will cooperate I will be taking pictures and see how it looks, also will possibly post them…

Dee

‘@Willow, you said it all!!!!!

Willow

Good morning all! Wouldn’t you love to sit on a stump and gaze at a moon looking like the one in the photo for this article?! WOW! Our God gives us such Awesome beauty!

terri

thanks, very interesting…learn something new EVERYDAY..

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