TWIN FALLS, Idaho (KMVT/KSVT) — Over the next few days you will hear a term called weather spring. It begins on March 1 each year and ends on June 1 each year. However, you may be used to spring starting at the end of March – on the 21st or 20th (depending on the year). You would be right to say that. So why are we talking about soring now?
If you asked an astronomer (someone who studies space), they would tell you that spring starts at the end of March, and that would be correct. As the earth revolves around the sun, the tilt of our axis affects certain areas that receive direct sunlight throughout the year.
During the northern hemisphere summer, the northern half of the earth tilts toward the sun, while the southern half tilts away from the sun. The result is more direct sunlight to the northern hemisphere.
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 is tilted towards the sun. The result is more direct sunlight to the southern hemisphere.
What happens on the first day of spring and fall? Everywhere on earth sees direct sunlight. They are called the equinoxes, and these two days (late September and late March) represent the first days of spring and fall.
Meteorologists look at the seasons a little differently though. Instead of basing this on the length of days and who sees the most direct sunlight, we just look at the typical weather conditions for 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.
For this reason, meteorologists unofficially consider the start of a season to be the first of every third month, with spring beginning March 1, summer beginning June 1, fall beginning September 1, and winter beginning September 1. 1st December. 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 say otherwise.
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