At least 10 people have died of the cold in Poland in recent days, officials said, with temperatures plummeting below minus 20C on Saturday.
Planes have been grounded and ferry services disrupted in several places across the continent.
Heavy snow in Istanbul forced Turkish Airlines to cancel more than 650 flights. The Bosphorus Strait was also closed and ferries stopped completely, according to the state-run Anadolu news agency.
Parts of southern Italy were reportedly buried beneath a metre of snow and in Rome the fountains in St Peter's Square froze overnight.
It has also been the coldest Orthodox Christmas in Russia for 120 years, with thermometers reading minus 30C overnight in Moscow, and minus 24C in St Petersburg.
In Greece's second-largest city, Thessaloniki, temperatures fell to minus 7C, and in Athens they reached 0C. Several Greek islands, including Lesbos, experienced heavy snowfall.
In the former Olympic ski resort of Sarajevo, in Bosnia, many skiers stayed away from the slopes as temperatures dipped to minus 27C, Sky News reported.
In Switzerland, the lowest temperature in western Europe was recorded in the village of La Brevine, which reached minus 29.9C on Friday.
The village also holds the record for the coldest-ever recorded temperature in Switzerland, of minus 41.8C on 12 January, 1987.
Additional reporting by AP
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