Spring Equinox

The first day of spring is when the sun shines directly on the celestial equator passing from south to north and the length of day and night are almost the same. This is also varyingly referred to as Astronomical Spring, the March Equinox or Vernal Equinox.

Astronomical Spring is determined by the changing positions of the earth relative to the sun giving us the solstices and equinoxes. Seasons are caused by the tilt of the earth on its axis by 23.5 degrees. The tilt of the earth does not change as it goes around the sun so in the Northern Hemisphere the earth is tilted toward the sun in June and away from the sun in December. When the sun is over the equator, you have the equinoxes. The March equinox occurs in the Northern Hemisphere between the dates of March 19 to 21.

Meteorological Spring is determined by the annual temperature cycles and the Gregorian calendar. Meteorological spring starts March 1st in the Northern Hemisphere and lasts 3 months (March, April, and May.) Many countries around the world (depending on their latitude) will use different methods to determine the start of spring. Some of these methods are dependent on the average daily/night temperatures, animal and plant behaviors, soil temperatures and their traditional calendar systems.