Spring is in the air - WMC Action News 5 - Memphis, Tennessee

Spring is in the air

MEMPHIS, TN (WMC) -

Spring is in the air and after the winter we've endured, it's about time. Astronomically speaking, the spring occurs when the most direct rays of the sun move north of the equator. 

In the northern hemisphere, this is known is known as the vernal equinox, and marks the start of the spring season. In the southern hemisphere, this equinox is known as the fall or autumnal equinox and marks the start of the fall season. 

The vernal equinox for the southern hemisphere occurs in September in the northern hemisphere it's fall. The vernal equinox or start of spring happens at the same moment around the world but is converted to local time. This year in the Mid-South spring begins on March 20 at 5:45 P.M. CDT.

From a meteorological standpoint, however, in the northern hemisphere the official spring season always begins on March 1 and continues through May 31. Meteorologists divide the year into quarters to make it easier to compare seasonal and monthly statistics from one year to the next. 

The meteorological seasons are based on annual temperature cycles rather than on the position of Earth in relation to the sun, and they more closely follow the Gregorian calendar. Using the dates of the astronomical equinoxes and solstices for the seasons would present a statistical problem because these dates can vary slightly each year.

The word equinox is derived from the Latin word "equi" meaning “equal" and "nox" meaning night. Around the world days and nights are approximately equal. On the vernal equinox the sun rises exactly in the east and sets exactly in the west. 

At the equinoxes the tilt of the Earth relative to the sun is zero, which means that Earth's axis neither points toward nor away from the sun. Although, the tilt of Earth relative to its plane of orbit, called the ecliptic plane, is always about 23.5 degrees.

Ron Childers, WMC Action News 5 Managing Meteorologist

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