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Meteorological winter has arrived. What does that mean?

A person paused to take in the sunset from the dock of the MIT sailing pavilion.Jessica Rinaldi/Globe Staff

It’s Dec. 1 and that means meteorological winter is officially underway. If you’re unfamiliar with the premise of the meteorological seasons it’s basically that the year is divided into quarters and December through February represent the coldest quarter of the year and therefore winter.

This obviously is different from the astronomical seasons you learned a school kid — they skew later and are based on the position of the sun.

Meteorological seasons are based on temperature, not the sun’s position.NOAA

Last week I gave my winter outlook which would encompass the entire winter. Meteorological winter does not include snowfall that occurs earlier in the fall or in March or April nor does it take into account late-season cold occurring in meteorological spring. In this piece I am going to present a lot of charts and data.

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It will give you an idea of how what has occurred so far this fall may play into our winter ahead and some of the trends due to climate change.

This year, meteorological autumn was the third-warmest on record in Boston. We were in the running for the warmest but the past five days knocked us back a couple of places.

Nevertheless, it’s been a warm year. Since June we’re running the warmest on record and of course it’s also been overall a wet year.

Meteorological Fall was warm and wet.NOAA

If you’re wondering if the warm fall has any implications for the winter there is definitely some correlation. If you look at the warmest September through November on record you’ll find that those years generally have less snow than average.

Statistics can be broken up into all sorts of ways but in general the weather of the past three months does portend less snow than average in Southern New England.

Winters with warm falls generally, although not always, have less snow than average.NOAA

Our winter months have been getting warmer. Check out the warm versus cold meteorological winters below. You will notice only two really cold winters since 2000, but multiple warm ones. There is an enormous difference between a winter with an average daily high in the 40s versus one around freezing.

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The winter of 2014-15 was the last really cold one in these parts.

The chart above shows the warmest and coldest meteorological winters on record for Boston.NOAA

This warming trend doesn’t mean we couldn’t have a colder-than-average winter ahead, but it does mean there is definitely less of a chance of a below-normal-temperature type of winter.

Finally, Dec. 1 is also the end of hurricane season. It was an active season in the Atlantic but not unusually active in the hemisphere. There were an above-average number of named storms, however it’s important to remember that storms are being named now that wouldn’t have been named 20 years ago, due to a change in criteria.

A look at the named storms of 2021.NOAA