In the Northern Hemisphere, the official spring season begins with the equinox on March 20th at 6:29 am. (EDT).
Astronomically speaking, the equinox occurs when the Sun crosses the celestial equator on its way north along the ecliptic. This March equinox is also known as the vernal, or spring, equinox, and marks the start of the spring season.
Meteorologically speaking, however, in the Northern Hemisphere the official spring season always begins on March 1 and continues through May 31. Summer begins on June 1; autumn on September 1; and, winter on December 1.