What Is the Spring Equinox?
In the Northern Hemisphere, the spring equinox (also called the March equinox or vernal equinox across the globe) occurs when the Sun crossesthe celestial equator going south to north. It’s called the “celestial” equator because it’s an imaginary line in the sky above Earth’s equator. Imagine standing on the equator; the Sun would pass directly overhead on its way north.
On the March equinox, the Northern Hemisphere and Southern Hemisphere receive roughly equal amounts of sunlight; neither hemisphere is tilted more toward or away from the Sun than the other.
Although in most locations (the North Pole and the equator being exceptions), the amount of daylight had been increasing each day after the winter solstice—and after the spring equinox, many places will experience more daylight than darkness in each 24-hour day. The amount of daylight each day will continue to increase until the summer solstice (in June), when the longest period of daylight occurs.
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Here’s an interesting fact: Equinoxes are the only two times yearly that the Sun rises due east and sets due west for all of us on Earth! While the Sun passes overhead, the tilt of Earth is zero relative to the Sun, which means that Earth’s axis neither points toward nor away from the Sun. (Note, however, that Earth never orbits upright but is always tilted on its axis by about 23.5 degrees.)
Read more about the reason for the seasons.
What Does “Equinox” Mean?
The word equinox comes from the Latin words for “equal night”—aequus (equal) and nox (night). On the equinox, the length of day and night is nearly equal in all parts of the world.
Spring Equinox FAQs
Q: Does Spring Begin on March 1 or on the Equinox?
A: Well, both. The answer depends on your definition of “spring.” Both dates are accurate; they’re just from different perspectives. We’ll explain …
Astronomically speaking, the first day of spring is marked by the spring equinox, which falls on March 19, 20, or 21. The equinox happens at the exact moment worldwide, although our clock times reflect a different time zone. And, as mentioned above, this date only signals spring’s beginning in the Northern Hemisphere; it announces fall’s arrival in the Southern Hemisphere.
Interestingly, due to time zone differences, there hasn’t been a March 21 equinox in mainland United States during the entire 21st century! We won’t see a March 21 equinox again until 2101.
Meteorologically speaking, the official first day of spring is March 1 (and the last is May 31). Weather scientists divide the year into quarters to make it easier to compare seasonal and monthly statistics from one year to the next. The meteorological seasons are based on annual temperature cycles rather than on the position of Earth in relation to the Sun. Meteorological seasons more closely follow the Gregorian calendar since using the dates of the astronomical equinoxes and solstices for the seasons would present a statistical problem as these dates can vary slightly each year.
