SKY · FIELD GUIDE
Full Moon Names, Supermoons & Blue Moons: Where They All Come From
Every full moon in the calendar carries a name — Wolf, Snow, Harvest, Cold — and every so often one gets called super, micro or blue. Who decided all this, and how much of it is astronomy versus tradition?
Open any moon calendar — including LEV's — and the full moons come dressed in names and badges: the Wolf Moon, the Harvest Moon, a supermoon here, a blue moon there. Some of that is astronomy you can measure. Most of it is tradition and definition — which is fine, as long as the calendar is honest about which is which.
The names: a farmer's calendar, not an astronomer's
The twelve names most English-language calendars use are traditional North American names popularised by the Old Farmer's Almanac, blending Native American, colonial and European seasonal traditions. January's full moon is the Wolf Moon (wolves heard in deep winter), February's the Snow Moon, March's the Worm Moon (the ground softening), then Pink (an early spring wildflower — not the Moon's colour), Flower, Strawberry, Buck (new antlers), Sturgeon, Corn, Hunter's, Beaver and Cold.
None of this is astronomy. The Moon in January is physically identical to the Moon in July. The names are a record of what each month's bright night meant to the people who worked under it — which is exactly why they've lasted.
The Harvest Moon: the one that moves
One name refuses to sit in a month. The Harvest Moon is the full moon nearest the September equinox — usually September's full moon, but roughly every third year it lands in early October instead (2025 is one of those years: the Harvest Moon falls on 7 October). When it does, September's moon stays the Corn Moon, and the Hunter's Moon — defined as the full moon after the Harvest Moon — slides a month later with it.
The name is earned by real geometry. Near the equinox, the full Moon's rising point tracks the shallowest angle of the year against the horizon at mid-northern latitudes, so it rises only ~25 minutes later each evening instead of the usual ~50. Before electric light, that run of bright, early-rising moons at exactly crop time was worth naming. LEV computes the Harvest Moon from the same equinox instant the seasons pages publish — one source of truth, so the two pages can never disagree.
Supermoons: real physics, fuzzy boundary
The Moon's orbit is an oval: around 356,000–370,000 km away at perigee, 404,000–406,000 km at apogee. When a full moon happens near perigee it genuinely is closer, larger (about 7% across) and brighter (roughly 15%) than average — that part is measurable physics, and the moon calendar prints the distance for every single full moon so you can see the orbit breathing through the year.
The fuzzy part is the word. "Supermoon" was coined by an astrologer, Richard Nolle, in 1979, and astronomy adopted it without ever agreeing on a line. Some lists use a distance threshold; some use Espenak's "within 90% of that orbit's perigee distance"; some count proximity in hours. A full moon at 361,000 km makes one list and misses another — nobody is wrong; they drew the line differently. LEV's badge uses the common ≤360,000 km form, states it, and shows the number, so a borderline moon is a visible judgement call rather than a silent verdict. The same applies in reverse to micromoons — full moons beyond ~405,000 km, the year's smallest-looking.
One more honest note: the enormous Moon you sometimes see sitting on the horizon isn't a supermoon effect. That's the Moon illusion — your brain, not the orbit — and it works on any moonrise.
Blue moons: a calendar accident with a good story
The Moon's full cycle takes 29.5 days; most months are longer. Slip a full moon into the first day or two of a month and a second one squeezes in before it ends — the blue moon in its popular sense. It happens about every two and a half years (next: 31 May 2026), and the Moon looks exactly as silver as ever.
The term's history is a comedy of errors: the older Maine Farmers' Almanac meaning was the third full moon in a season that has four; a 1946 Sky & Telescope article misread it as "second in a month," and the mistake stuck so thoroughly that it's now the definition everyone uses. A Moon that literally looks blue is possible — but only through wildfire smoke or volcanic ash with particles of just the right size to scatter red light, as happened after Krakatoa.
What the calendar promises
Every time on the moon phase calendar is the published minute from the US Naval Observatory, cross-checked by LEV's own computation; every distance is computed and verified against JPL's planetary ephemeris; every name and badge is attributed to the tradition or definition it comes from. The astronomy is measured. The folklore is labelled as folklore. Both are worth having — you just deserve to know which is which.
Frequently asked questions
Where do the full moon names come from?
The names most calendars use — Wolf, Snow, Worm, Pink, Flower, Strawberry, Buck, Sturgeon, Corn, Hunter's, Beaver, Cold — are traditional North American names popularised by the Old Farmer's Almanac, drawing on Native American, colonial American and European seasonal traditions. They're designation facts, not astronomy: the Moon behaves identically in January and June; the names track what the season meant to the people naming it — wolves heard in midwinter, fields ready at harvest.
What makes the Harvest Moon different from the others?
It's the one name not fixed to a month. The Harvest Moon is defined as the full moon nearest the September equinox — usually September's, but roughly every three years it falls in early October instead. When that happens, September's full moon keeps its Corn Moon name and the Hunter's Moon (defined as the full moon after the Harvest Moon) slides later too. What earned it the name: around the equinox, the Moon rises only ~25 minutes later each night instead of the usual ~50 at mid-latitudes, giving farmers a run of bright early evenings at exactly harvest time.
What is a supermoon, exactly?
A full moon that happens near perigee, the closest point of the Moon's oval orbit — so it looks a little larger and brighter than average. There is no single official definition: the term came from astrology (Richard Nolle, 1979), and astronomers have adopted several competing thresholds. LEV's calendar uses a common distance form — a full moon closer than 360,000 km — and prints the distance on every row, so when different lists disagree about a borderline moon, you can see exactly why.
How much bigger does a supermoon really look?
About 7% larger across and around 15% brighter than an average full moon, and up to ~14% larger than a micromoon at the other extreme. Side by side the difference is obvious; in the sky on its own, most people honestly can't tell. The famous 'huge moon' near the horizon is the Moon illusion — a trick of perception that works on every moonrise, super or not.
Is a blue moon actually blue?
No — the name is calendrical, not optical. In its popular modern sense, a blue moon is the second full moon inside one calendar month, which happens because the Moon's cycle (29.5 days) is slightly shorter than most months. The older almanac definition — the third full moon in a season that has four — is where the term started, before a 1946 magazine article's misreading gave us the monthly version everyone now uses. A moon can genuinely appear blue, but only through smoke or volcanic ash of just the right particle size.
Why do different sites give slightly different supermoon lists?
Because they use different definitions. A distance threshold (like 360,000 km) gives one list; Fred Espenak's 'within 90% of that orbit's perigee distance' gives a slightly longer one; others count anything within a day of perigee. A full moon at 361,000 km makes some lists and misses others — nobody is wrong, they're answering differently-drawn lines. That's why the calendar prints the actual distance instead of asking you to trust a badge.
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