Article by www.farmersalmanac.com
The first day of spring will occur on Saturday, March 20, 2021, at 5:37 a.m. EDT for those of us in the Northern Hemisphere, which is marked by the arrival of the vernal (spring) equinox.
Traditionally, we celebrate the first day of spring on March 21, but astronomers and calendar manufacturers alike now say that the spring season starts on March 20th, in all time zones in North America. In 2020, spring fell on March 19th, the earliest first day of spring in 124 years!
Regardless of what the weather is doing outside, the equinox marks the official start of the spring season.
What does Vernal Equinox Mean?
Vernal translates to “new” and “fresh,” and equinox derived from the Latin aequus (equal) and nox (night).
So what does that mean? Essentially, our hours of daylight—the period of time each day between sunrise and sunset—have been growing slightly longer each day since the winter solstice in December, which is the shortest day of the year (at least in terms of light).
Even though we know that after December 21st, the days start getting steadily longer, we still see more darkness than light over the course of a day. The vernal equinox marks the turning point when daylight begins to win out over darkness.
At this moment, the direct rays of the Sun are shining down on the equator producing the effect of equal day and night (give or take a few minutes). After the vernal equinox, the direct rays of the Sun migrate north of the Equator (with hours of daylight steadily growing longer) until they finally arrive at the Tropic of the Cancer (latitude 23.5 degrees north).