Pull out the woolly hat and gloves because winter is just around the corner.
Winter is only a few weeks away now meaning our days are about to get a lot shorter and a lot colder.
And to top that off – the clocks are going back this weekend meaning once again the long trudge home from work, school or university will be in the dark.
So when does winter technically start? Here is everything you need to know.
When is the start of winter?
Winter starts on December 1 this year AND December 21.
How do we determine the start of winter?
We technically start winter twice every year because the season begins on different dates on the meteorological and astronomical calendars.
The reason for measuring the start of winter (and other seasons) on two calendars rather than one is two-fold.
The meteological calendar is based on calendar months meaning the seasons are equal in length and begin on the same date each year.
Astronomical seasons meanwhile take into account the Earth’s 23.5 degree tilt on its rotational axis and its orbit around the sun.
Both have their strengths. Experts use the meteological seasons to compare seasonal and monthly statistics while the astronomical seasons are arguably a better gauge of temperature and weather conditions.
Okay. When is the winter solstice?
(Picture: Met Office)
The winter solstice is marked on the astronomical calendar and starts this year on December 21.
Spring and autumn equinoxes (equal day and night) and the summer (longest day) and winter (longest night) solstices mark the start of the astronomical seasons each year. The word ‘equinox’ itself actually mean ‘equal’ (equi) and ‘night’ (nox). The solstice meanwhile is when the sun reaches its highest or lowest point in the sky at noon.
The dates of these change each year as they are dependent on the Earth’s position. The earth is closest to the sun, known as perihelion, in early January and furthest away, aphelion, in early July.
When does winter end?
Winter will end on the meteological calendar on 28 February 2017.
On the astronomical calendar winter ends 19 March 2017 with the spring equinox.
Which is the better measure?
While the astronomical seasons might give a better idea of when temperatures will get colder, the meteorological calendar is a lot easier to use when comparing one season to the last.
This is due to the seasons being equal length each year compared to the wildly varying season lengths with the astronomical calendar.
The Met Office, for example, and other forecasters around the world use the meteorological definition of seasons as this ‘determines a clear transition between the seasons’.