Spring starts Thursday all over America, which is weird

Pablo Tucker
March 19, 2020

The first day of spring usually arrives on March 20th or 21st, but it's coming early this year as a variety of factors fall into place.

From late March to late September, conversely, the South Pole is angled away from the Sun, so that the Sun is positioned more directly over the northern hemisphere, reaching its highest point in the northern sky (and lowest in the southern sky) on or around June 22. For the US the 2020 equinox falls on March 19, making it the earliest since 1896. Perhaps you learned as a child that the spring equinox - when day and night are roughly the same length - occurs on either March 20 or March 21. This cycle of seasons occurs as the Earth makes its complete revolution of the sun approximately every 365 days. As the US National Weather Service explains, the "nearly" equal hours of day and night are because of the complex way a sunrise is measured and the refraction of sunlight in our atmosphere.

In 2016, the spring equinox in the Eastern time zone was at 12:30 a.m. on March 20, which means it was at 9:30 p.m. on March 19 in the Pacific time zone.

What could the weather hold for spring in the U.S.?

Which hemisphere you're in at the time determines exactly which kind of equinox you're experiencing.

The Earth is tilted on its axis.

The exact timing of the equinoxes and solstices changes from year to year, simply due to slight variations in Earth's orbit around the Sun. "In fact, it's 365.24 [days]".

The longer answer involves leap years.

When we added February 29 to the calendar this year, it pushed the calendar forward for everything after, and thus shifted the timing of every celestial event like this back a day, compared to last year.

But did you know that doesn't happen EVERY four years? The leap day turns back the clock on the time of the equinox, almost resetting the approximately six-hour annual leap forward from the previous three years. That's because the Earth's 574,395,530-mile annual orbit of the sun really takes 365.2422 days.

The equinox gets later each year and then "jumps back" on the next leap year.

The solstice also is the shortest day of the year in the Southern Hemisphere. People who lived most of their lives in the 20th century became accustomed to observing the equinox on March 20 or 21.

But on the equinoxes, the sun's most direct rays are right over the equator.

Again: 1900 wasn't. But 2000 WAS.

A day-old lamb explores new surroundings on the first day of spring, March 20, 2019, at Coombes Farm in Lancing, England.

But all that time, the equinox was slowly getting earlier by about 45 minutes every four years.

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