Britons marked the winter solstice today with a swim at the beach and yoga sessions outside an 11th century castle to witness the dawn after the longest night of the year as hopes continued to build for a white Christmas.

A brave swimmer took a swim at Portobello Beach, Edinburgh. Other early birds joined a Yoga session at Corfe Castle of the National Trust in Dorset for the dawn.

The northern hemisphere’s winter solstice is when the sun begins to set.

This comes at a time when parts of Britain are facing a whiteout Christmas. Snow is expected to begin falling tonight and continue until Christmas Day. However, it’s still unclear which areas will be hardest hit.

Northern Ireland and Scotland are most likely to experience a white Christmas on 25 December, particularly on higher ground. Temperatures could drop to as low as -6C (21F).

This comes just three nights after Britain’s coldest winter night. It was -9.3C (13F) at Braemar, in the Cairngorms, last night. That follows -9.1C (15.6F), on Sunday, and -8.9C (16F), on Saturday in the same village. 

(From left) Charlotte Gardiner, Sasha Udell, Andrea Taylor, Clare Donoghue, Patricia Yeyti and Agnes Pachacz take part in a winter solstice swim at Portobello Beach in Edinburgh today to witness the dawn after the longest night of the year

Sasha Udell and Charlotte Gardiner take part in an evening swim at Portobello Beach today in Edinburgh to watch the dawn of the longest day.

People gather on Glastonbury Tor in Somerset this morning on the day of the winter solstice to watch the sun rise

Glastonbury Tor is a Somerset landmark where people gather to see the sunrise on this winter solstice morning.

People take part in a winter solstice yoga session at the National Trust's Corfe Castle in Dorset to mark the solstice today

Participants take part today in the winter solstice yoga class at Corfe Castle, National Trust.

People gather on Glastonbury Tor this morning on the day of the winter solstice in the northern hemisphere

This morning, thousands of people gather at Glastonbury Tor to celebrate the Winter Solstice in northern hemisphere.

The winter solstice for the northern hemisphere marks the start of astronomical winter and the day with the shortest amount of daylight - Shetland being the most extreme example with just five hours and 49 minutes

For the northern hemisphere, the winter solstice marks the beginning of astronomical winter. Shetland is the extreme case with only five hours and 49 seconds of daylight.

This graphic from the Met Office shows cold air moving in from the north, but milder air heading in from the south-west

This graph from Met Office depicts cold air coming in from north and milder air going in from south.

However, the Met Office acknowledged that the exact boundary of cold and warm air is still not known. They stated that they were unsure where snow can be expected over Christmas.

Tomorrow’s conditions are expected to get more unstable, and rain bands will be seen across the UK. Before more snow on Thursday, sleet and snow are expected to prevail over the higher ground of Scotland.

What will it be like in the UK on Christmas Day?

These odds are provided by William Hill for Christmas Day snow at airports below.

Edinburgh: 4-9

Leeds-Bradford: 4-9

Newcastle: 10-11

Birmingham: 10-11

Manchester: 10-11

Glasgow: 6-5

Liverpool: 11-8

Belfast: 2-1

Cardiff: 9-4

Bristol: 11-4

London Gatwick: 11-4

London City: 11-4 

Due to the strong winds, Blizzards may be possible in Scotland Christmas Eve. William Hill is a favourite of Edinburgh and Leeds, while Newcastle, Birmingham and Manchester are all close behind at 10-11.

Some areas further south will remain cloudy and mild with some rain. Additionally, there’s a risk of fog crossing southern England and Wales on Christmas Eve.

The Met Office is uncertain about where Britain’s snow ‘boundary’ might be – between snowy and non-snowy parts of the country – but its official Christmas outlook, predicted Scotland is the most likely place to see snow.

Strengthening northerly winds at Christmas Eve will push the boundary.

You will feel colder and there is a chance for blizzards at high elevations. 

The south has mild weather, but cloudy skies and rainy spells from the west.

For the Christmas period, severe weather warnings may be issued because of the forecasted ‘blizzard” for Scotland.

Through the week temperatures will fall, and overnight freezes can reach as low as 6C (21F).

Helen Caughey is the Met Office’s deputy chief meteorologist. She said that because colder air meets milder over the UK the details of Christmas Day forecast are still uncertain.

“Milder air is moving north-east across most of the country in the middle of week with occasional rain. This will eventually turn into snow on higher ground in northern Scotland.

People take part in a winter solstice swim at Portobello Beach in Edinburgh this morning to mark the occasion

To mark this occasion, people take part in an early morning winter solstice swimming at Portobello Beach in Edinburgh

A woman feels the cold as people take part in a winter solstice swim at Portobello Beach in Edinburgh this morning

As people participate in the winter solstice swimming at Portobello Beach, Edinburgh this morning, a woman experiences the cold

(Left to right) Agnes Pachacz, Sasha Udell, Charlotte Gardiner and Andrea Taylor at Portobello Beach in Edinburgh today

Left to right, Agnes Pachacz and Sasha Udell with Charlotte Gardiner, Andrea Taylor, at Portobello Beach today in Edinburgh

Charlotte Gardiner, Sasha Udell, Andrea Taylor, Clare Donoghue, Patricia Yeyti and Agnes Pachacz in Edinburgh today

Charlotte Gardiner (Sasha Udell), Andrea Taylor and Clare Donoghue are among the many people who visited Edinburgh today.

People take part in a winter solstice swim at Portobello Beach in Edinburgh this morning to witness the dawn

To witness the sunrise, people take part in an early morning winter solstice swimming at Portobello Beach in Edinburgh.

Swimmers take part in a winter solstice swim at Portobello Beach in Edinburgh this morning mark the day

This morning, swimmers take part in the winter solstice swimming at Portobello Beach in Edinburgh.

People take part in a winter solstice swim in Edinburgh today to witness the dawn after the longest night of the year

To see the sunrise after the longest night, people take part in the winter solstice swimming in Edinburgh.

Swimmers go into the water for a winter solstice swim at Portobello Beach in Edinburgh this morning

This morning, swimmers take to the sea at Portobello Beach, Edinburgh for a winter solstice swimming session

The boundary between milder and colder atmospheres is expected to fall south during Christmas Eve and Christmas Day. Some will experience colder, clearer weather.

“However, it is difficult to pinpoint exactly where that boundary is at this time. This is crucial for determining where snow can be expected over Christmas.

William Hill, Bookmaker today named Edinburgh and Leeds as his top 4-9 picks for white Christmas in 2021. In addition to this, all thirteen major UK airports have dropped to their lowest point in over a decade.

According to the company, the collective book for a white Christmas was 11-4. This is significantly lower than what happened in 2010 when snow fell on nearly all stations. However, 19% of the stations also had snow.

Rupert Adams (William Hill spokesperson) said, “Although it may seem ironic,” that forecasters have begun to embrace the idea of white Christmas.

People take part in a winter solstice yoga session at the National Trust's Corfe Castle in Dorset this morning

Participants take part this morning in a yoga class at Corfe Castle, National Trust, Dorset.

National Trust's Corfe Castle in Dorset is pictured as people take part in a winter solstice yoga session this morning

National Trust Corfe Castle, Dorset, is photographed as participants in this morning’s winter solstice Yoga session

Corfe Castle, pictured today, dates back to the 11th century and was one of the first to be built at least partly from stone

Corfe Castle (pictured today) dates back at least to the 11th Century and is one of the earliest to have been built from stone.

People take part in a winter solstice yoga session at the National Trust's Corfe Castle in Dorset this morning

This morning, people took part in winter solstice Yoga at Corfe Castle of the National Trust in Dorset

Corfe Castle's hilltop position helps make it a popular tourist destination - and a yoga session was held there today

Corfe Castle is a hilltop location that makes it an attractive tourist spot. Today, a yoga class was held at the castle

People take part in a winter solstice yoga session at the National Trust's Corfe Castle in Dorset this morning

Participants take part this morning in a yoga class at Corfe Castle, National Trust, Dorset.

People take part in a winter solstice yoga session at Corfe Castle in Dorset to mark the solstice this morning

To mark the winter solstice, people take part in an evening of yoga at Corfe Castle, Dorset.

There has been some quiet confidence in the prospects, although it was kept behind closed doors for some while, many people have not been willing to risk their reputation.

“As soon as the five-day deadline for forecasting snow fell, people calling the snow day became a lot louder. Therefore punters are enjoying a festive frenzy of renewed confidence.

According to the company, all it takes to declare a white Christmas technically is for one snowflake to fall in any of the 13 UK airports.

Although there have been four white Christmases over the last six years, they only involved a few locations.

William Hill added that since 1960, there have been only four occasions when at least 40 per cent of UK weather stations have reported snow on the ground at 9am on December 25 – those being 1981, 1995, 2009 and 2010.