The meteorological system is the simpler and more practical approach for climatology, weather forecasting, and agricultural planning. It divides the year into four seasons of three full calendar months each, based on the annual temperature cycle.
For most practical, day-to-day purposes (planning, clothing, agriculture, energy use), the meteorological 3-month season is preferred. For traditional or celestial events, the astronomical system remains authoritative. Neither is wrong; they simply serve different functions.
Because the Earth’s orbit is elliptical rather than a perfect circle, the lengths of these seasons vary slightly, ranging from . 2. The Meteorological Definition (Exactly 3 Months)