You may have heard us mention the words "Meteorological Spring" several times. That's because with the start of March is the start of a new season... sort of.
Technically, Spring does not begin until March 20, when the sun passes directly above the equator. It's known as the Vernal Equinox. If we follow the astronomical calendar, then we have a wide range of season lengths, due to the elliptical path of the Earth's orbit around the sun. The length would vary from 89-93 days.
But meteorologists and climatologists like to keep things simple and group together months together based on the annual temperature cycle. March, April and May are considered meteorological spring, and they have much more similar characteristics when it comes to temperature and weather patterns than say, March 20 through June 21, when (as you know) it already feels like it's well into summer.
Plus, the season length is less varied, running from 90-92 days.
Having this consistency in both length of the season and temperature makes it much easier to compare data that is helpful in agriculture and forecasting.