When Does Winter Start?

Being a country girl, I’ve always known when the shortest day and the longest day is, and the start dates of each season and so on.  Or so I thought.

December Solstice (Winter Solstice) is on Tuesday, December 22nd 2015 at 4:49 AM in London. This day is 8 hours, 49 minutes shorter than on the June Solstice. In most locations north of Equator the shortest day of the year is around this date.  The earliest sunset this year is on December 13th 2015.

Sunset 21st Dec 14
There was this incredible sunset last year on 21st December 2014

How you define the first day of winter, however, depends on whether you are referring to the astronomical or meteorological winter.  The day in our calendar that marks the first day of winter usually refers to the astronomical seasons which are a result of the Earth’s axis and orbit around the sun. However, the Met Office often uses a meteorological definition of the seasons.  Astronomical seasons are relative to the position of the Earth’s orbit around the sun taking into account equinoxes and solstices. Meteorological seasons are instead based on annual temperature cycles measuring the meteorological state and coinciding with the Gregorian calendar to determine a clear transition and equal length of season.

Sunrise 20th Jan 2015
And we saw some stunning January sunrises in 2015

Meteorological winter season

This year the meteorological winter begins on 1 December 2015 and ends on 29 February 2016. The meteorological seasons consists of splitting the seasons into four periods made up of three months each.  These seasons are split to coincide with our Gregorian calendar making it easier for meteorological observing and forecasting to compare seasonal and monthly statistics. By the meteorological calendar, winter always starts on 1 December.  The seasons are defined as Spring (March, April, May), Summer (June, July, August), Autumn (September, October, November) and Winter (December, January, February).

Astronomical winter season

This year the astronomical winter begins on 21 December 2015 and ends on 20 March 2016.  The astronomical calendar determines the seasons due to the 23.5 degree tilt of the Earth’s rotational axis in relation to its orbit around the sun. Both equinoxes and solstices are related to the Earth’s orbit around the sun.

Solstices and equinoxes are considered to be the astronomical transition points between the seasons and mark key stages in the astronomical cycle of the earth. In a year there are two equinoxes (spring and autumn) and two solstices (summer and winter). The dates of the equinoxes and solstices aren’t fixed due to the Earth’s elliptical orbit of the sun. The Earth’s orbit around the sun means that in early January, the sun is closest (known as perihelion) and in early July it is most distant (aphelion).

Many moons ago my village school taught me the seasons astronomically and until recently I had only a very basic knowledge of the meteorological seasons at all.  In fact I found myself getting into an argument with friends over it, which is why I’m writing this now.

There is of course also a third theory of how the seasons work, and it’s the one I can relate to the most.  It’s based on what we can actually see around us, and it’s the one that farmers and countrymen use.  It’s true that some years Spring manifests itself earlier than in other years, depending on the weather conditions; sometimes it’s very late.  And the same can be said of every season.  Mother Nature controls the weather and the seasons follow accordingly.

Just yesterday, on 17th December 2015, whilst on a Christmas shopping trip to our county town, Mr Midlife and I were astounded to see that the beautiful willow trees overhanging the River Witham which runs through the town centre were still in full leaf.  Yes, some of those leaves were a little yellow, and a few were lying on the river bank, but most of them were still blowing in the breeze attached to their branches,  Unbelievable considering that we have had howling winds for many days, strong enough to blow roofs off.  What an incongruous sight it was, to have the willows defying the seasons on the left hand side of our view, yet to the right we were watching children dressed in hats and gloves skating on a real ice rink which has been especially installed for the Christmas period in the market square.  But then it has been an incredibly mild Autumn.  Unfortunately I didn’t have my camera with me.

There’s blossom on some of the town garden trees I noticed, and I shouldn’t be surprised if the hedgerows were to burst into leaf before New Year.  Absurd.  Every year there are elements of Nature that astound and mystify me, which is why I think my understanding of the seasons will continue to be defined by what my natural world looks like when I’m out and about.  And roll on 22nd December next week, as it will be getting a little lighter every day thereafter.  Fact.

(Many thanks to the Met Office website and to http://www.timeanddate.com for the above facts and dates.)


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