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SALT LAKE CITY — Thanks to the state’s fifth-warmest winter on record, it’s felt like spring in Utah for the past few months already.
But Tuesday, it became official.
The vernal equinox, which occurred March 20 this year at 10:15 a.m., marked the first day of spring in the northern hemisphere.
So, what is an equinox?
An equinox is one of two moments during the year when the sun is exactly above the Earth’s equator, and day and night are the same length, according to the Encyclopedia Britannica.
The vernal equinox marks the beginning of spring and occurs around March 20 or 21 when the sun moves north across the equator. The autumnal equinox marks the beginning of fall and occurs around Sept. 22 or 23 when the sun crosses the equator going south.
There are a few reasons why the dates vary from year to year, but one of the main reasons is because a year is not an even number of days, and neither are the seasons.
The calendar tries to come as close as possible to the exact length of the year by giving a close approximation to the tropical year, which is the actual length of time it takes the Earth to complete one orbit around the sun.
Another reason is that the Earth’s elliptical orbit is constantly changing its orientation to the sun, causing the Earth’s axis to point in different directions. The seasons begin when the sun is located at a strict 90-degree interval. Because of Earth’s skewed positions, it reaches the location that begins the new seasons at different times each year.
The pull of gravity also affects the location of Earth in its orbit, and thus affects the seasons’ beginnings.
What is weather usually like in Salt Lake City on the first day of spring?
The hottest first day of spring on record was in 2017 at 75 degrees Fahrenheit. The coldest was in 1965 at 17 degrees Fahrenheit, according to the Weather History and Data Archive.
Tuesday, the average temperature is 50 degrees Fahrenheit with a high of 60 degrees and a low of 39 degrees. In 2017, the first day of spring was an average of 62 degrees Fahrenheit with a high of 75 degrees and a low of 49 degrees.
On the first day of spring ten years ago, the average temperature in Salt Lake City was 45 degrees with a maximum temperature of 57 degrees and a minimum of 33 degrees.
So for those hoping to get in some spring skiing before the season ends — thank your lucky stars (or earth's rotations) that it's not colder!