On Sunday, we can really say spring has begun with the arrival of the vernal (or spring) equinox, which occurs March 20 at 12:30 a.m. Eastern time. Read more in-depth explanations here: http://wapo.st/1MrztSd
  1. The equinox is the “official” first day of spring
    Humans have long celebrated the equinoxes and solstices as seasonal turning points. Yet while people often refer to the equinox as the first “official” day of spring, there is no universally agreed upon definition for the seasons. Astronomers and physicists define seasons by the solstices and equinoxes, while for meteorologists and climate scientists, spring is defined by annual temperature cycles, and begins on March 1.
  2. You can balance an egg on its end on the equinox
    Urban legend has it you can keep an egg balanced upright at the exact moment of the equinox. This practice likely has roots in Chinese lunar new year traditions, but in reality has no scientific basis. With a bit of luck (and patience), you can balance an egg upright on any day of the year.
  3. Sunrise and sunset are exactly 12 hours apart
    Though equinox means “equal night” in Latin, both of Earth’s hemispheres get a bit more than 12 hours of daylight. Take Washington, D.C., for example: On March 16 — four days before the equinox — sunrise and sunset were exactly 12 hours apart. Yet by March 20, the sun is already up for 12 hours and 9 minutes.
  4. The spring equinox is always on March 20
    The exact time of the equinox varies from year to year, which means so can the date. To avoid confusion between time zones, the time of the equinox is usually based on Coordinated Universal Time (UTC), which is four hours ahead of Eastern Daylight Time. By this metric, the vernal equinox can occur anywhere from March 19 to March 21.
  5. Spring is generally warmer than fall.
    After the cold days of winter, we tend to expect spring weather to be warm and sunny. While it often feels warm compared to winter, spring isn’t as warm as you might expect. Not only is the spring equinox typically colder than the fall equinox in September, but in most of the Lower 48, spring on the whole is a few degrees cooler than fall (based on the meteorological seasons).