Spring Starts Tonight - 5 Facts about the Equinox

Spring in the northern hemisphere begins tonight - Tuesday, March 19th at 11:06 AM EDT.

1. The equinox occurs when the sun is directly over the equator resulting in a nearly equal length of night and day for nearly every region of the world.

2. It is called the Vernal Equinox because the word "vernal" stands for Spring and "equinox" means "equal night" in Latin.

3. It doesn't happen on the same day every year and instead is usually within 4 days from March 19-23. It is because a calendar year is 365 days but it takes Earth 365.25 days to revolve around the sun. That extra quarter adds up (and is part of the reason we have a leap day) and means the equinox fluctuates around 6 hours yearly. For example, in 2024 the equinox was on March 20th.

4. Meteorological Spring is different than astronomical Spring. Because the Spring equinox fluctuates it is easier to group the seasons by the first of the month for record-keeping. Meteorological Spring is the months of March, April, and May with meteorological summer starting June 1 (the summer solstice is June 20th).

5. The Spring Equinox determines a couple of holidays: it is the first day of the first month of the Iranian solar calendar and is the start of the Persian New Year. Also, Easter is determined as the first Sunday following a full moon after the solstice (which for simplicity is marked as March 21)

Before we jump into Spring we wanted to look back at some of the more impactful moments of (meteorological) winter 2023-2024.