Weekend Weather Blog: What is meteorological spring?

Published: Feb. 26, 2022 at 9:32 PM MST
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TWIN FALLS, Idaho (KMVT/KSVT) — Over the next few days, you’ll hear a term called meteorological spring. It begins every year on March first and ends every year on June first. However, you may be accustomed to spring beginning in late March - on the 21st or 20th (depending on the year). You would be correct in saying that. So why are we talking about soring now?

If you were to ask an astronomer (someone who studies space), he or she would tell you that spring begins at the end of March, and that would be correct. As the earth orbits the sun, the tilt of our axis affects certain areas that see direct sunlight throughout the year.

During the northern hemisphere summer, the northern half of the earth is tilted toward the sun, while the southern half is tilted away from the sun. The result is more direct sunlight to the northern hemisphere.

Axis tilt June-Aug
Axis tilt June-Aug(Nicholas Snider)

Conversely, during the northern hemisphere winter (late December to late March), the northern half of the earth is tilted away from the sun, and the southern half of the earth of is tilted toward the sun. The result is more direct sunlight toward the southern hemisphere.

Axis tilt winter
Axis tilt winter(Nicholas Snider)

What happens during the first day of spring and fall though? Everywhere on earth sees direct sunlight. These are known as the equinoxes, and these two days (in late September and late March) represent the first days of spring and fall.

Meteorologists look at the seasons a bit differently though. Instead of basing this off of the length of days and who sees the most direct sunlight, we simply look at the typical weather patterns of each month. How often do you see the thermometer reach 90° in early June? Quite often - about as often as you see snow in early December.

Because of this, meteorologists unofficially consider the beginning of a season on the first of every third month, with spring beginning on March 1, summer beginning on June 1, fall beginning on September 1, and winter beginning on December 1. So the next time you hear the term meteorological spring, the earth’s position around the sun may not be ready yet, but the weather may be saying otherwise.

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