Spain has seen unseasonably warm weather over the Christmas period
National records have fallen in eight countries - and regional records in another three.
Warsaw, Poland, saw 18.9C (66F) on Sunday while Bilbao, Spain, was 25.1C - more than 10C above average.
The mild European weather comes as North America faces more severe storms, days after a deadly winter cold snap left more than 60 dead.
Heavy snow and freezing rain have been forecast for parts of the northern Midwest while severe thunderstorms and tornadoes are expected in Texas, Oklahoma, Arkansas and Louisiana.
But on the European side of the Atlantic, the weather has been balmy for many places at the start of the year.
Temperatures in the Netherlands, Liechtenstein, Lithuania, Latvia, Czech Republic, Poland, Denmark and Belarus broke national records.
Station records were broken in Germany, France and Ukraine.
The temperature recorded in Warsaw on 1 January was 4C higher than the previous record for the month, and Belarus' record high was 16.4C, some 4.5C above the previous record.
In Spain, New Year's Day temperatures in Bilbao were equivalent to the average in July, and parts of Catalonia including Barcelona are subject to restrictions on water use.
Records are broken all the time, but it is unusual for the difference to be more than a few 10ths of a degree.
In Switzerland, temperatures hit 20C, and the warm weather has affected ski resorts across the Alps which have seen a snow shortage.
It's not all warm in Europe, though - colder temperatures and snow are forecast in parts of Scandinavia and Moscow is expected to drop to -20C by the weekend.
Warm temperatures mean cherry blossom has come early to the Polish city of Szczecin
Just days earlier, the UK, Ireland, France and Spain declared 2022 their hottest year on record.
In the UK, every month but December was hotter than average. December itself saw snow fall across large parts of the country, although conditions are milder and wetter now.
Heatwaves have become more frequent, more intense, and last longer because of human-induced climate change.
However, winter events such as these do not have the same human impact as summer heatwaves, which can result in large numbers of excess deaths.
The world has already warmed by about 1.1C since the industrial era began and temperatures will keep rising unless governments around the world make steep cuts to emissions.
-- Courtesy of BBC News