10 Things To Know About The Spring Equinox

Many parts of the country have already had teases of spring-like weather, but the actual first day of the new astronomical season will come this Friday.

Here are 10 things to know about the spring, or vernal, equinox.

1. Spring's beginning on Friday will depend on where you live: If you're in the Eastern time zone, then spring officially begins on Friday at 10:46 a.m. local time. That means that spring will start at 9:46 a.m. in the Central time zone, 8:46 a.m. in the Mountain time zone and 7:46 a.m. in the Pacific time zone.

2. Here's why there's a down-to-the-minute time that marks spring's beginning: Twice a year, in late March and late September, the sun's rays shine directly over the equator. In the Northern Hemisphere, these are known as the spring, or vernal, equinox and the fall, or autumnal, equinox.

The specific time, which in the case of this year will be 10:46 a.m. EDT, marks the passage of direct sunlight over the equator from the Southern Hemisphere to the Northern Hemisphere.

3. Day and night are balanced on the equinox and daylight will now increase: Instead of a tilt away from or toward the sun, during an equinox, the Earth's axis of rotation is perpendicular to the line connecting the centers of Earth and the sun.

Because of that, day and night are balanced to nearly 12 hours each all over the world. You can see this in the satellite image below, which shows the half sunlit and half nighttime (dark areas) parts of the world during the March 20, 2022, equinox.

From this point on, daylight in the Northern Hemisphere will gradually grow longer until the summer solstice, which occurs on June 21 this year. That's because Earth will be in the process of tilting toward the sun in the Northern Hemisphere.

4. Everything is opposite for the Southern Hemisphere: South of the equator, the March equinox marks the beginning of fall.

Daylight will now grow shorter until June's start of winter in places like Australia and South America as Earth tilts away from them.

6. The sun rises due east and sets due west: The vernal equinox is one of only two times per year (the other being the autumnal equinox) when the sun rises directly in the east and sets directly in the west from every location on Earth. If you have a compass, it's a great time to take it out and test it!

7. The word "equinox" means "equal night": The term comes from the Latin words "aequus" (equal) and "nox" (night), referring to the approximately equal length of day and night that occur during it.

8. You can observe the equinox effect with a simple shadow experiment: On the equinox, a vertical stick or pole creates a unique shadow pattern that occurs only twice per year. If you place an upright stick in the ground (called a "gnomon," from the Greek word meaning "to know") and track the tip of its shadow throughout the day, you'll discover something remarkable: the shadow tip traces a perfectly straight line from west to east.

This straight-line shadow path is exclusive to equinox days. At all other times of the year, shadow tips follow curved paths across the ground. To try this yourself, find a level, sunny spot and either use an existing flagpole or plant a straight stick vertically in the ground. Mark the shadow tip's position every hour or so with small stones or stakes. By day's end, your markers will form a straight line running west to east.

The shadow behavior differs by location: In the Northern Hemisphere, this straight shadow line passes north of your stick, while in the Southern Hemisphere, it passes south. At the equator, the midday shadow disappears entirely, because the sun passes directly overhead at solar noon. By conducting this simple experiment, you can demonstrate the same astronomical principles that ancient civilizations used to track seasons and build their calendars.

9. Different cultures celebrate the equinox in unique ways: The spring equinox has served as a cornerstone for cultural celebrations across many civilizations. In Iran and much of Central Asia, Nowruz (meaning "new day") marks the Persian New Year, and begins precisely at the moment of the vernal equinox. This 3,000-year-old celebration, recognized by UNESCO as an Intangible Cultural Heritage of Humanity, involves families gathering around the Haft-Sin table with seven symbolic items beginning with the letter "S" in Persian, representing renewal and rebirth.

Japan observes Shunbun no Hi (Spring Equinox Day) as a national holiday. During this time, Japanese families visit ancestral graves, clean tombstones and offer flowers and food to honor their ancestors. The holiday reflects Buddhist and Shinto beliefs about the balance between the spiritual and physical worlds, with many temples holding special ceremonies.

10. Daylight changes accelerate after the equinox: Following the spring equinox, the Northern Hemisphere gains daylight at its fastest rate. This occurs because the sun crosses the celestial equator at its steepest angle relative to the horizon. During this time, small changes in Earth's orbital position translate to large changes in daylight duration. For example, mid-latitude locations can gain 2-3 minutes of daylight per day in the weeks following the equinox, with the effect being most dramatic between 30-60 degrees north latitude. This acceleration gradually slows as we approach the summer solstice in June, when the rate of daylight change reaches zero.

Senior writer Chris DeWeese edits Morning Brief, The Weather Channel’s newsletter.