TERRE HAUTE, Ind. (WTHI) - Believe it or not Spring has already started.

At least what is called meteorological spring has started. What’s the difference between meteorological spring and the Spring season that is marked on the calendar?

Right now the Wabash Valley is right in the middle of the first days of two Spring seasons. Meteorlogical spring started March 1st. However the calendar shows Spring starting on March 20th.

What’s the difference between these two types of spring? Meteorological Spring is what the scientific community uses as the spring season based on temperature cycles. For scientists Spring is March April, and May. It is much easier to calculate seasonal weather stats when the seasons are broken up into clean three month groups.

The Spring season most people use however is begins March 20th. This is called "Astronomical Spring." Astronomical Spring starts on the Vernal Equinox when the Earth is between the Winter Solstice and Summer Solstice (the shortest and longest days of the year).

The beginning and end of Astronomical seasons that we use on calendars can fall on different days so it’s less useful for scientists to calculate seasonal stats when the Spring days can be different.

Ultimately, the Spring season meteorologists use is based on the annual temperature cycle and the spring the calendar uses is based on the position of the earth around the sun.