The Met Office has issued new weather warnings for heavy snow as the UK is hit by an air mass from Scandinavia - but what does that mean?

Temperatures will drop and forecasters have warned of travel chaos, power cuts and "widespread ice" as well as potential injuries from slips and falls.

Up to 40cm of snow could fall in the coming days in some parts of the country and "freezing rain" is set to hit parts of east Wales and the north Midlands.

The South East has so far escaped weather warnings, but temperatures are still expected to plunge to 0C.

What have the Met Office said?

Met Office Deputy Chief Meteorologist, Jason Kelly, said: “While the south of the UK hangs onto the milder air for much of this week as we approach the weekend, the area of low pressure responsible for the snow across the north of the UK will clear, allowing colder air to push south and west across much of the country."

Why are we having this cold snap?

A spokesman from The Met Office told us: "At the moment Scotland and northern England are more likely being influenced by a Polar Continental Air Mass (from Scandinavia) but because a weather front has become stationary across these areas that’s why we are seeing rain and snow there.

"Meanwhile, Wales and the rest of England are experiencing southwesterly winds and therefore a Tropical Maritime Airmass, hence it is much milder here.

The Argus: The UK is set to be hit by a huge winter storm (Image: WXCHARTS)The UK is set to be hit by a huge winter storm (Image: WXCHARTS)

"As we head to the weekend it is more likely that most of the UK will be experiencing easterly winds rather than northerly winds, so we are not really expecting an Arctic Blast but more of a Polar Continental Air Mass."

What is a Polar continental Air Mass?

This air mass has its origins over the snow fields of Eastern Europe and Russia and is only considered a winter (November to April) phenomena.

During the summer with the land mass considerably warmer, this air mass would be classed as a tropical continental.

The weather characteristics of this air mass depend on the length of the sea track during its passage from Europe to the British Isles: this air is inherently very cold and dry and if it reaches southern Britain with a short sea track over the English Channel, the weather is characterised by clear skies and severe frosts.

With a longer sea track over the North Sea, the air becomes unstable and moisture is added giving rise to showers of rain or snow, especially near the east coast of Britain.

The lowest temperatures across the British Isles usually occur in this air mass, lower than -10 °C at night, and sometimes remaining below freezing all day.

What is the forecast in the South East? 

Wednesday:

A spell of rain will likely linger through the morning, especially in the south and east. Some afternoon brightness in the west but also a few showers. Maximum temperature 10C.

Outlook for Thursday to Saturday:

Thursday and Friday, some bright spells but also some showers, heavy at times. Saturday, further spells of rain likely, perhaps turning wintry later as colder northeast winds develop.

Outlook for Sunday to Tuesday: 

Rather cloudy and cold across the UK on Sunday with wintry showers over eastern parts. An area of high pressure then looks to build to the north, and it will likely feel cold or very cold, especially in brisk easterly winds. There is a chance of conditions being dry at times with widespread overnight frosts, although wintry showers can still feed in from the east coast.

Any organised areas of cloud and precipitation arriving from the southwest will not progress very far into the country as a result of the high pressure. However, they can bring the potential for widespread snow across areas where they bump into cold air. Patches of ice and other disruptive wintry hazards remain a possibility for all areas.

The Met Office revealed last month was the coldest January in 10 years.

The average temperature last month was 2.2C, the service said in a blog post.

This makes it the coldest January since 2010, when the average was 0.9C.

The coldest January on record was 1963, when conditions averaged -1.9C.