The Winter Solstice is just days away...but did winter already start?
40s, 30s, 20s, teens, single digits...you name, we've seen it all over the past month. The days have gotten shorter. Temperatures have dropped. All signs that winter has begun. But the real start to astronomical winter is still a few days away!
The winter solstice marks the beginning of the astronomical winter season. But, there is a second winter timeline: meteorological winter. Why have two different "winters"? Meteorological seasons are broken up into four 3-month periods based upon annual temperature cycles. In the northern hemisphere, winter is the coldest time of the year. Thus, meteorologists view December 1st as the start of winter and February 28th as the end (except for leap years which push it to February 29th). By grouping the months in accordance to their temperature cycle, it is also easier for meteorologists and climatologists to keep more accurate records.
The difference between the meteorological and astronomical seasons are simply the fact that Earth's orbit around the sun does not land on the 1st of the month. This year, the winter solstice falls on December 21st (at 11:28am EST). This solstice is observed when the Earth's position is such that the sun is directly over the Tropic of Cancer.
So the debate goes on. But whether you think winter starts on the 1st or the 21st, we're certainly in for some more chilly days!
-Meteorologist Zack Green