Autumn Equinox 2027: the first day of fall

What the autumn equinox is

The September equinox is the moment the Sun crosses the celestial equator heading south, when its ecliptic longitude reaches 180 degrees. For that instant the Earth's axis leans neither towards nor away from the Sun, the noon Sun stands directly over the equator, and day and night are close to equal everywhere. In the Northern Hemisphere it is the start of astronomical autumn, or fall; south of the equator it is the start of spring.

In 2027 the moment is 23 Sept, 06:01 UTC, which is 2:01 AM EDT on Thursday, September 23, 2027 where you are. From now until the March equinox, the nights are longer than the days in the Northern Hemisphere, and the Sun rises a little farther south each morning.

Day and night, and the equilux

On the equinox in New York there are 12h 07m of daylight, a few minutes more than 12 hours. Sunrise and sunset are timed by the top edge of the Sun's disc rather than its centre, and the atmosphere lifts the Sun's image by about half a degree near the horizon, so the Sun is visible for several minutes longer than the geometry alone says.

The day with the closest to exactly 12 hours of daylight, the equilux, comes a few days after the September equinox in the Northern Hemisphere. In New York it is Sunday, September 26 (11h 59m); in London it is Saturday, September 25. Near the equator there is no equilux, because the day never drops to 12 hours.

The days shorten fastest now

Day length changes fastest around the equinoxes. Around this one, New York loses about 2.7 minutes of daylight a day and London about 3.9; in Reykjavik, much closer to the Arctic Circle, it is about 6.4 minutes a day. The decline slows through November and stops at the winter solstice in December, the shortest day.

East and west, and the Sun among the stars

The equinox Sun rises almost exactly due east and sets almost exactly due west, from everywhere except the poles. At noon it stands 49.1° above the horizon in New York, which is 90 degrees minus your latitude. At the North Pole the Sun sets around now for six months; at the South Pole it rises. The equinox point was named the First Point of Libra 2,000 years ago, but precession has carried it into the constellation Virgo, where the Sun sits on the day.

Aurora season

Aurora watchers look forward to the equinoxes. On average, geomagnetic storms are more frequent in the weeks around the March and September equinoxes, because at those times the tilt of Earth's magnetic field lines up best with the magnetic field carried by the solar wind (the Russell-McPherron effect). Add the returning dark nights in the north, and late September is one of the best times of year to see the northern lights.

The Harvest Moon

The full moon closest to the September equinox is the Harvest Moon. In 2027 it is on Wednesday, September 15, full at Wed, Sep 15, 7:04 PM New York time. What makes it special is how it rises. Normally the Moon rises about 50 minutes later each night. Around the autumn equinox, though, the evening Moon is moving along the part of its path that makes the shallowest angle with the eastern horizon, so it rises only a little later from one night to the next. In New York around this year's Harvest Moon the moonrise comes only about 22 minutes later each evening, compared with about 71 minutes around the full moon nearest the spring equinox. Before electric light that meant several bright evenings in a row, just when farmers needed to bring in the harvest. The full moon after it is the Hunter's Moon. See all of them on the moon calendar or check the next full moon.

Autumn equinox traditions

Mabon and harvest festivals

Modern Pagans celebrate the autumn equinox as Mabon, the second of three harvest festivals on the Wheel of the Year, between Lughnasadh in August and Samhain at the end of October. The name was given to the festival in the 1970s by the American writer Aidan Kelly, borrowing Mabon ap Modron, a figure from Welsh legend; it is a modern name, not an ancient one. It is a time of thanksgiving for the harvest and of balance between light and dark. Older harvest customs are still kept: the English Harvest Home supper after the last load was brought in, and church Harvest Festivals, which became popular in Victorian Britain and are often held in late September or early October.

Higan in Japan

The autumn equinox, Shubun no Hi, is a national holiday in Japan; in 2027 it is on Thursday, September 23. Like the spring equinox it is the centre of Higan, a seven-day Buddhist period for visiting family graves and remembering ancestors. In autumn the rice cakes eaten are called ohagi, named after the bush clover that flowers in this season, and the red spider lilies known as higanbana bloom along paddy fields and riverbanks right on time.

Chuseok and the Mid-Autumn Festival

Two of East Asia's biggest holidays are harvest moon festivals. China's Mid-Autumn Festival and Korea's Chuseok are both held on the 15th day of the 8th month of the lunisolar calendar, the night of the full moon. Families gather to admire the Moon, eat mooncakes in China and songpyeon rice cakes in Korea, where Chuseok is a three-day holiday with ancestral rites and visits to family graves. Because the 8th lunar month is defined by the Chinese calendar, the festival usually lands on the Harvest Moon but sometimes on the full moon before it. In 2027 the two coincide: the festival is on September 15, and that night's full moon is the Harvest Moon. Vietnam's Tet Trung Thu, with lanterns for children, is held on the same night.

Chichen Itza and Sukkot

The light-and-shadow serpent on the stairway of El Castillo at Chichen Itza in Mexico appears on late afternoons around the autumn equinox as well as the spring one. In the Jewish calendar, Sukkot, the harvest Festival of Booths, begins on the 15th of Tishrei, at the full moon of that month in September or October, five days after Yom Kippur.

Southern Hemisphere: the spring equinox

For Australia, New Zealand, South Africa and South America the September equinox is the spring equinox, the first day of astronomical spring, and the days lengthen from here. The southern equilux comes a few days before it. The southern autumn equinox is the March equinox, next on Saturday, March 20, 2027 (UTC). Set your city above to see the right numbers for you.

Astronomical vs meteorological fall

Astronomical fall runs from the September equinox to the December solstice, about 89.9 days. Meteorological fall is September, October and November. Fall is shorter than summer because Earth speeds up as it heads towards its closest point to the Sun in January. The seasons page lists the length of every season and every equinox and solstice to 2030. In Reykjavik the equinox brings 12h 13m of daylight; in London 12h 10m.