SPRINGFIELD, Mass. (WWLP) – December 1 marks the start of meteorological winter, but in most calendars, the cold and snowy season doesn’t start until December 21. There is one pretty simple reason for the difference in start times, and it all has to do with making keeping weather and climate records an easier experience.
The Earth takes 365.24 days to travel around the sun, which is why every 4 years we created Leap Years. Because of that, the exact start date and time of solstices and equinoxes vary from year to year. That, and the elliptical shape of Earth’s orbit around the sun, change the astronomical seasons to vary from 89 to 93 days. And that changing start date and time to the different seasons makes it much harder to consistently compare weather and climate statistics from year to year. So, to make that more simple, meteorologists think of the seasons in 3-month periods.
Winter is December through February, spring is March through May. Summer is June through August, and autumn is September through November.