Exactly 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 date seems to change every year.
It changes because the first day of spring is also the vernal equinox – “spring” and “equal night” – which changes every year. Although spring usually starts on March 20 or 21.
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 sees 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.
So, when does spring start? This year spring start as 7:02 am on Wednesday, March 20.