First Day of Spring Facts: Is It Arriving Earlier?
Snow melting, flowers blooming earlier in U.S., research shows.
It may not feel like it in the chilly United States, but it's the first day of spring in the Northern Hemisphere.
The season officially begins at 12:57 p.m. ET on March 20—a precise and fixed point in time defined as when the center of the sun passes directly over the Equator. (See "Vernal Equinox Pictures: First-Day-of-Spring Celebrations.")
But biological signs of spring's arrival are a different science, defined by the timing of events—such as the first appearance of flowers—that change from year to year and place to place.
According to a long-term research project done in Colorado's Rocky Mountains, for instance spring in that region now begins, on average, about three weeks earlier than it did in the 1970s.