Vernal Equinox

Spring begins with the vernal equinox on March 20 at exactly 1:32 P.M. EDT. 

The word equinox is derived from the Latin for “equal night” and is used now because the days and nights are of nearly equal length. The vernal equinox is the point at which the center of the Sun passes over the celestial equator from south to north, signaling the start of nature's renewal in our hemisphere. 

After the equinox, the Sun will appear higher and higher in the sky, and length of day will grow longer than the length of night. (Farmer’s Almanac)

Here is a lovely poem welcoming Spring by Swinburne:

For winter's rains and ruins are over, And all the season of snows and sins; The days dividing lover and lover, The light that loses, the night that wins; And time remembered is grief forgotten, And frosts are slain and flowers begotten, And in green under wood and cover Blossom by blossom the spring begins. Algernon Charles Swinburne (1837–1909) Atalanta in Calydon (1865)