CORPUS CHRISTI, Texas — Although the calendar says spring begins March 20th, today is the beginning of Meteorological Spring. So what is the difference?
Astronomical seasons are based on the position of Earth in relation to the sun while the meteorological seasons are based on the annual temperature cycle.
The beginning of Astronomical Spring or the Vernal Equinox marks the time when the sun passes directly above the equator. The date of the Vernal Equinox varies and can fall anywhere from March 20-22nd.
Earth actually travels around the sun in 365.24 days so an extra day is needed every fourth year, which we call Leap Year. This causes the exact date of the solstices and equinoxes to vary. Also, the elliptical shape of Earth’s orbit around the sun causes the lengths of the astronomical seasons to vary between 89 and 93 days.
These variations in season length start date make it difficult to consistently compare climatological statistics for a particular season from one year to the next. So that is why the meteorological seasons are used.
Meteorological seasons are used primarily for the documentation of climate information. Each season is an even 3-month period, falling more in line with our civil calendar.
March 1st through May 31st is Meteorological Spring, June 1st through August 31st is Meteorological Summer, September 1st through November 31st is Meteorological Fall and December 1st through February 28th is Meteorological Winter.
This year, Spring officially begins on March 20th at 12:33 PM at the time of the Vernal Equinox.