SYRACUSE, NY (WSYR-TV)- Meteorologists refer to December 1 as the start of the winter season but the calendar says it starts December 21. What’s the difference?
Meteorologists break down every season into a 3 month time period based on temperature. Meteorological winter is December, January and February. This breakdown is more precise, consistent and makes it easier to calculate yearly seasonal statistics. This is helpful when comparing weather patterns which is really helpful for those in the agriculture and commerce fields.
The astronomical calendar defines winter, or the winter solstice, as a day when the sun passes directly above 23.5°S latitude or the Tropic of Capricorn. It’s the day in the Nothern Hemisphere when we have the shortest amount of daylight hours. Since it takes the Earth just over 365 days to travel around the sun, we have a leap year every four years. This causes astronomical season lengths to vary, according to the NWS, between 89 and 93 days. The start dates also vary.
Simply put, meteorological winter is based on the annual temperature cycle and astronomical winter is based on the position of earth in relation to the sun.