When is the winter solstice?

The winter solstice is almost upon us, marking the shortest day of the year and the start of astronomical winter.

Meteorological winter started on 1 December but some prefer to wait for the solstice before they mark the beginning of the season.

Technically speaking the solstice is a specific moment, not a whole day and in 2025 it happens at 15:03 on 21 December.

It is a moment many people look forward to as it means that from this point forward the days will start to get longer and we experience more daylight.

The word 'solstice' comes from the Latin sol, meaning 'sun', and sistere - to 'stand still'.

The winter solstice is the moment the Sun appears to stand still, directly above the Tropic of Capricorn, the most southerly latitude it reaches annually.

This gives the southern hemisphere its longest day of the year with the Sun reaching its highest angle in the sky.

It leaves the northern hemisphere with less sunlight and consequently its maximum amount of darkness.

We have solstices because the Earth is tilted on its axis by 23.5 degrees, which affects which part of the planet's surface the sun is directly overhead at any given time.

After the winter solstice the Sun begins to move north again relative to the equator until eventually - six months later - it reaches it most northerly point, overhead the Tropic of Cancer, and gives us the summer solstice.

Midway between the two solstices we have the equinoxes where the sun is directly over the equator.

The date of the winter solstice can vary slightly from year to year.

This is because Earth takes around 365.24 days (give or take a few decimal places) to complete an orbit around the Sun - so not an exact year.

It means the timing of the solstice slips by about six hours each year, which adds up to a full day over four years.

At this point we observe a leap year, an extra day in the calendar, allowing the solstice to revert to its earlier date.

Other factors that influence the timing of the solstices include variations in the length of the Earth's orbit, and a wobble in its axis caused by its rotation.

Due to the tilt of the Earth the winter solstice will mean shorter days at higher latitudes.

In the UK the day will be shorter the further north you are, and you can check the exact sunrise and sunset times for your location on the BBC Weather website and app.

Within the Arctic Circle - down to a latitude of 23.5 degrees from the North Pole - the sun will not rise at all.

This depends on how we define the seasons.

Meteorological winter starts on 1 December - approximately three weeks before the solstice - and runs until the final day of February.

This is because weather forecasters divide the year into four equal chunks of three months each, with spring running from March to May, summer from June to August and autumn from September until November.

It means weather records are standardised, using the same dates every year, allowing for straightforward analysis of changes in the climate over time.

However the astronomical seasons are defined by the Earth's position in its orbit, marked out by the solstices and equinoxes.

And so by this criteria, the winter solstice is the first day of winter.