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Spring equinox: Here's what you should know about the first day of spring

Last supermoon of 2019 lights up the sky

By the end of the day, spring will officially have sprung — even if it doesn't feel like yet it in your city. March 20, 2019, marks the spring equinox — the first official day of spring in the Northern Hemisphere. This day is unique in that the length of day and night are close to equal, NASA explains.

Spring equinox doesn't always land on March 20, but it will always hold the same meaning: a brand new season. Here's what you should know about the spring equinox.

What is an equinox?

Equinox means "equal night" in Latin. And on the autumnal and spring equinox, that's exactly what happens — there are equal parts day and night. The Earth's orbit puts in just the right place so that it's lined up with the sun, according to NASA. On the equinox, which happens twice a year, both hemispheres receive the same amount of daylight. While the spring equinox occurs in the Northern Hemisphere, the autumnal equinox is occurring in the Southern Hemisphere.

The spring equinox could occur on March 19, 20 or 21, depending on the year. Six months later, the autumnal equinox will occur. 

seasons msg 2010 11 lrg by APOD Videos on YouTube

The time-lapse video above compresses the Earth's year-long orbit in about 12 seconds — during which both the spring and autumnal equinoxes occur.

When exactly is this year's spring equinox?

Contrary to popular belief, a groundhog does not determine when winter will end and spring will start. The spring and autumnal equinox, as well as summer and winter solstice, occur at precise times determined by the Earth's orbit around the sun. Seasons are caused by the fact that the Earth is tilted on its axis by 23.5 degrees, according to the National Weather Service. This year's spring equinox will occur at exactly 5:58 p.m. EDT on March 20. 

What will change?

While you may not immediately notice obvious signs of spring, they will be there. For several days before and after the equinox, the length of daylight will range from about 12 hours, six and a half minutes, to 12 hours, 16 minutes, depending on where you are in relation to Earth's equator. The days will become a bit longer at the higher latitudes, further from the equator, because it takes a bit longer for the sun rise and set.

You might not feel warm rays of sun peeking through lush trees yet, but rest assured, spring weather is right around the corner for the Northern Hemisphere.