The Siberian weather front has blanketed much of Europe in snow.
Much of Britain and Ireland was blanketed in snow on Wednesday as freezing Siberian
weather dubbed "the Beast from the East", disrupted the travel plans of thousands.
Hundreds of schools were closed and there were delays on roads, railways and at airports.
Temperatures fell to minus 12 Celsius (10 degrees Farenheit) in some rural areas while Britain's weather service warned of up to 40 cm of snow in higher areas of Scotland.
"It is the coldest air we have seen over the UK at this time of the year since around 1991," Becky Mitchell, a meteorologist at Britain's Met Office, said.
The cold spell has been caused by a jump in temperatures high over the Arctic, known by meteorologists as sudden stratospheric warming, which has weakened the jet stream that brings warm air in from the Atlantic to Ireland and Britain.
The unusual weather could continue as Storm Emma, packing more snow and ice, approaches western England from Portugal and France.
Across London, there were severe delays on public transport and dozens of flights were cancelled at Heathrow airport.
Britain's weather service issued a severe weather warning for snow in parts of Scotland where schools were closed and council offices shut.
Ireland's weather service issued a status red warning - the highest level of alert - for five countries in the east, including the capital Dublin after heavy overnight snowfall led to accumulations of 5 to 10 cm. Ireland could see its worst snow since 1982.
In southern Romania, an 83-year-old woman from Adancata was found collapsed in the snow and died on the way to hospital, the Institute for Emergency Situations said.
More than 80 trains and 15 flights were cancelled, Romanian police said, and Romania's Black Sea ports were closed.
Record snowfall of 182 cm (72 inches) paralysed the northern Croatian town of Delnice and rescue services took several hours to evacuate residents in the nearby village of Mrzle Vodice.
Schools were closed in Bucharest and ten Romanian counties as well as across western and central Croatia.
The roofs of dozens of houses collapsed under the weight of snow in the Unsko-Sanski canton in northwestern Bosnia.
State-run RTCG TV reported that Montenegro's main Golubovci airport was closed for several hours overnight.