Seasonal weather records are officially organized by meteorological season. These are slightly different than the seasons you see marked on calendars.
Our planet takes 365.25 days to complete a revolution around the sun. As a result, the exact dates for the beginning of the astronomical seasons – equinoxes and solstices – vary from year to year. To maintain consistent records, meteorologists use groupings of three whole-months to subdivide the year. These quarters are based on temperature rather than the position of the Earth in its orbit.
In the northern hemisphere, for example, the meteorological winter begins on December 1st and includes the three coldest months of the year, December, January, and February. The winter solstice, on the other hand, does not arrive until December 21st or 22nd, depending on the year. This year’s meteorological winter recently made headlines as the fourth warmest on record.
In general, the four meteorological seasons arrive about three weeks ahead of the astronomical ones.
Graphics Credit: MF at The Weather Gamut