Autumn equinox 2024: When is it and what does it look like?

Technically, summer isn't over yet, but fall is upon us. There are specific times when the astronomical seasons officially change – in fall, it's the autumnal equinox. In spring, it's the vernal equinox.

The autumn equinox occurs in September in the Northern Hemisphere and for many marks a welcome change of seasons after a long, hot summer. But what exactly is an equinox? It's all about the Earth and its relationship with the Sun. Here's how to understand, visualize and celebrate the autumn equinox.

What is the autumn equinox?

The meaning of Equinox is already in the name: a combination of the Latin words for “equal” and “night”.

“There are only two times of the year when the Earth's axis is tilted neither toward nor away from the Sun, resulting in 'nearly' equal amounts of daylight and darkness at all latitudes,” the National Weather Service explained in a statement on the seasons.

The Earth rotates on an axis (imagine a line running from pole to pole) and the planet has a jaunty tilt of 23.5 degrees. The tilt creates the seasons. As the Earth orbits the sun, the tilt means that some areas of the planet get more direct sunlight than others. So it can be summer in the Northern Hemisphere (tilted toward the sun) and winter in the Southern Hemisphere (tilted away from the sun) at the same time. During the equinoxes, the sun shines directly on the equator, giving both hemispheres equal love.

Other planets that are also tilted on their rotation axis also experience equinoxes. However, the time scales can vary greatly. On Saturn, an equinox only occurs about every 15 Earth years. This means that on Saturn, each season lasts over seven years. On Neptune, it's even wilder, where seasons last decades. We can be thankful for the relatively short seasons on our planet.

When is the autumn equinox?

The autumn equinox in the Northern Hemisphere falls on September 22nd this year. If you want to know exactly when it is and mark it on your calendar, mark 5:44 a.m. PT.

The dates of the equinoxes may shift slightly from year to year, but they always occur around this time in September. The next vernal equinox in the Northern Hemisphere will occur on March 20, 2025, marking the beginning of spring.

What does the September equinox look like?

Wherever you are on Earth on the day of the equinox (and whether it's a spring or fall equinox depends on which hemisphere you live in), the sun will rise as far east and set as far west as possible, making it a foolproof compass. Go outside and watch sunrise and sunset, and memorize the landmarks in front of the sun – that way you'll always know exactly what is west and what is east.

The two equinoxes of the year also feature the fastest sunrise and sunset of the year, with the sun taking just a few seconds to appear and disappear. This is because this is the steepest angle at which the sun rises and sets during the year.

How is equinox different from solstice?

Like equinoxes, solstices are linked to the tilt of the Earth, but instead of day and night being evenly long, day and night are extremely long. The winter solstice is the shortest day of the year, while the summer solstice is the longest. The winter solstice falls on December 21 in the Northern Hemisphere this year.

Observing equinoxes from space

Orbiting Earth observation satellites have a unique view of the equinox. A video from NASA's Earth Observatory shows Earth from space and how the position of sunlight changes with the changing seasons. It's a great way to visualize what's happening as our planet orbits the sun.

How to celebrate the autumn equinox

Equinoxes aren't like solar eclipses or meteors. There's no big wow moment when you see something spectacular. The fall equinox will look like any other day this year, but it's a practical way to mark the change in astronomical seasons. You can go around and proclaim, “It's officially the first day of fall!” How you celebrate is up to you. Here's a suggestion: Put on your favorite sweater, take a scenic drive through the leaves, and sip a pumpkin latte to welcome fall in style.