When is the First Day of Spring?

Astronomically speaking, spring begins on the vernal equinox, usually March 20 in the USA and the rest of the Northern Hemisphere and September 22 or 23 in the Southern Hemisphere. Some Asian cultures call the vernal equinox “mid-spring” which is scientifically more correct, based on the angle of the sun, but here in the U.S., we refer to March 20 as the first day of spring.