When Does Spring Start?
Spring starts with the vernal equinox -- when there are exactly the same number of hours of daylight and darkness.
So, just when is the first day of spring?
The time and date seem to change every year — that's because the first day of spring is also the vernal equinox, which means “spring” and “equal night,” and changes every year.
This year, spring officially started at 7:02 a.m. today, March 20.
The vernal equinox means that that are exactly 12 hours of daylight and 12 hours of darkness in the Northern Hemisphere – the same as the autumnal equinox in the Southern Hemisphere. That’s when the sun passes directly overhead at noon if you are standing on the equator.
The two equinoxes also see the sun rise due east and set due west during the year.
In spring, the axis of the Earth tilts toward the sun. That increases the number of daylight hours, which brings warmer weather and sprouts new growth.