Britain will have to endure freezing temperatures as a wintry spell dubbed the "Beast from the East" grips the country, the Met Office has said.
With snow set to cause disruption, the mercury expected to plummet, and a storm poised to roll across the UK, here are some of the questions and answers surrounding the weather.
What has the Beast from the East been caused by?
Met Office Forecaster Craig Snell said the Beast from East has been caused by an event two weeks ago called sudden stratospheric warming.
This involved a huge rise in air temperature of around 50C in an area around 18 miles above the Earth in the North Pole.
What effect did this have?
Mr Snell said sudden stratospheric warming causes a weakening of the jet stream and allows cold air from western Russia to "flood" over Europe.
"It is going to remain over us for at least the rest of this week," he added.
As a result of the warming event, he also revealed that parts of the Arctic have also been up to 20C above normal temperatures.
How low will temperatures drop?
Mr Snell said there could be overnight lows of -15C recorded in Eastern Scotland and North East England on Wednesday and Thursday where there is lying snow.
He told the Press Association that daytime midweek temperatures will hover around freezing in most places across the UK.
The Met Office has said parts of the country "could see their coldest spell of weather since at least 2013, and possibly since 1991".
What is Storm Emma?
Storm Emma is a weather system which has impacted the Portuguese Islands called the Azores - and as a result has been named by their Met Service.
The weather front is expected to be disruptive when it arrives in the UK on Thursday - bringing blizzards, gales and sleet as it hits the cold air brought down by the Beast from the East.
Mr Snell said that without the cold air, and if there were normal or average UK temperatures, Storm Emma would instead have caused wet and windy conditions.
How unusual is the current weather?
Mr Snell said "highs and lows meet all the time", and added: "It is not too uncommon to see low pressures bumping into this air."
He said there is just a "quite noteworthy cold spell across the UK which is making it more interesting".