"We can't say definitively at this stage that 2015 will be the hottest one (year) on record - it hasn't ended yet - but it's very, very, very likely. We would really have to smash all low temperature records in December for it not to be the hottest year," said Clare Nullis, spokesperson of the WMO.
The December global temperatures would have to be 0.81 degrees celsius below average, colder than the current lowest temperature ever which was seen in December 1916, for 2015 not be the hottest year on record.
A very powerful El Nino is also responsible for the global shooting up of temperatures the effects of which will last into 2016, the WMO warned.
"We are seeing record sea temperatures and very, very warm land temperatures," Nullis said.
The November average global temperature across land and ocean surfaces was 0.97 degrees celsius above the 20th century average - the highest for any November between the period 1880 and 2015.
The November globally averaged sea temperature was 0.84 degrees celsius above the 20th century average - again, the highest for any November between 1880 and 2015.
Temperatures over the Arctic have risen by 2.9 degrees celsius since start of the 20th century.
"It's (temperature rise) really very rapid and widespread warming over the Arctic and its something we are obviously very acutely concerned about," Nullis said.
