1. Executive Summary Meteorological seasons are a method of dividing the year into four distinct periods—Winter, Spring, Summer, and Autumn—based on the annual temperature cycle and the calendar month. Unlike astronomical seasons, which are defined by the Earth’s axial tilt and solstices/equinoxes, meteorological seasons are fixed to specific dates for consistency in climate analysis, weather forecasting, and statistical record-keeping. This report outlines the definition, timing, scientific rationale, advantages, and limitations of meteorological seasons. 2. Introduction The concept of seasons is fundamental to understanding weather patterns, agriculture, ecology, and human activity. However, the traditional astronomical definition (varying dates around March 20, June 20, September 22, and December 21) introduces variability that complicates year-over-year climate comparisons. To address this, meteorologists and climatologists developed a simplified, fixed system: meteorological seasons . 3. Definition and Timing Meteorological seasons are defined by grouping complete calendar months into three-month periods that best reflect the typical temperature progression for the Northern Hemisphere (the Southern Hemisphere follows the opposite six-month offset).
| Season | Meteorological Months (Northern Hemisphere) | Corresponding Astronomical Period (approx.) | |--------|---------------------------------------------|----------------------------------------------| | Spring | March, April, May (MAM) | March equinox to June solstice | | Summer | June, July, August (JJA) | June solstice to September equinox | | Autumn | September, October, November (SON) | September equinox to December solstice | | Winter | December, January, February (DJF) | December solstice to March equinox | meteorological seasons