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The nights are drawing in, Christmas displays are already up in shop windows and you may already have turned the heating on. It certainly feels as though winter is on the way.

But when does the UK's coldest season actually start? The answer is: it depends on how you define it.

There are two common ways to define seasons in the UK - meteorological and astronomical.

´óÏó´«Ã½ Weather uses the meteorological calendar, where winter always begins on 1 December and ends on the last day of February.

Meteorologists use three-month periods to define the seasons. This makes year-on-year comparisons easier. Winter is therefore defined in the northern hemisphere as the three coldest months - December, January and February.

By comparison, in the astronomical calendar, winter always starts at the winter solstice - or shortest day.

This year, astronomical winter in the northern hemisphere begins on 21 December and ends on 20 March 2025.

There is a third definition used in some parts of the UK, particularly Northern Ireland: in the ancient Celtic calendar, also known as the Gaelic or Irish calendar, winter starts on 1 November.

The winter solstice is a key point in the astronomical calendar and marks the change from autumn to winter.

Astronomical seasons are based on the position of the Earth in relation to the Sun.

The Earth's axis is tilted at an average of 23.5 degrees. As the Earth travels on its year-long path around the Sun it is tilted towards or away from the Sun, which gives us our seasons.

When the North Pole is tilted towards the Sun, it is summer in the northern hemisphere.

In December, the winter solstice marks the exact moment the northern hemisphere is tilted the furthest away from the Sun. This is the shortest day of the year with the fewest hours of daylight.

The exact moment of the winter solstice varies from year to year due to a slight misalignment between the Gregorian calendar and the actual rate of the Earth’s rotation around the Sun, but it usually falls on 21 or 22 December.

The big freeze of 1963 was the coldest winter on record with snow from December to February.

But the UK does not often experience very cold weather. Occasionally, winters can be so mild that one might argue it never truly arrived.

February 2019 brought an exceptional spell of warmth to England and Wales with temperatures exceeding 20C more than once. With climate change, mild winters are becoming more common. In recent years, records have been shattered across Europe too.

In January 2023, temperatures reached an all-time high in a number of European nations. Warsaw in Poland, known for its cold winters, warmed up to 19C.

The trend of milder, mostly snow-free winters has held steady for many years. .

However, spells of extreme cold in the UK are still possible, even with climate change. In 2018, the infamous Beast from the East, which affected many parts of Europe, lasted well into meteorological spring.

However, a warming world means .