RICHMOND, Va. (WRIC) — Today is the first day of March and the start of meteorological spring. But wait a minute, doesn’t spring start on March 20? It does, but we have two springs to discuss.
March 1 is the unofficial meteorological beginning of spring based on annual temperatures. However, the official astronomical start to spring in the Northern Hemisphere is on Saturday, Mar. 20 at 5:37 am.
So, what’s the difference? The short answer: Meteorological spring is based on the annual temperature cycle and astronomical spring is based on the position of the Earth in relation to the sun.
Meteorologists and climatologists divide the seasons into three-month groupings where temperatures are similar. For example, meteorological spring is March, April and May because temperatures are consistent. In Richmond, temperatures are typically in the 50s, 60s and 70s on a regular basis during those months.
Astronomical spring is the official start of spring and it correlates with the vernal equinox. On or around March 21 is when the earth’s axis is tilted neither towards, nor away, from the sun resulting in equal amounts of daylight and darkness at all latitudes. The word equinox gives it away. Equinox is derived from the Latin words aequus (equal) and nox (night).