Meteorological Spring and Astronomical Spring are two ways of defining the start of spring, but they are based on different criteria.

Meteorological Spring refers to the three calendar months of March, April, and May in the Northern Hemisphere (or September, October, and November in the Southern Hemisphere). These months are considered to be spring because they generally have milder temperatures and more rainfall than the preceding winter months, and the days start to become longer.

Astronomical Spring, on the other hand, is based on the position of the Earth in relation to the sun. It is defined as the moment when the sun crosses the equator and day and night are of equal length. This event, known as the Vernal Equinox, usually occurs around March 20th in the Northern Hemisphere (or September 22nd in the Southern Hemisphere).

While Meteorological Spring is more closely tied to weather patterns and seasonal changes, Astronomical Spring is a celestial event that is fixed in time and based on the position of the Earth in relation to the sun.

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