The northern hemisphere winter , December 2014 to February 2015, was the warmest in the records, according to NASA.
The average temperature, taken for northern land and ocean surfaces, was
0.79°C above the 20 century average.
This was the highest for December, January and February in the 1880–2015 record, passing the previous record of 2007 by 0.03°C.
It is interesting to note that there were some 'cold spots'.
Eastern North America was colder than average, and there is an obvious 'blue blob' in the North Atlantic - which continued through 2015.