The city averaged a temperature of -15 C last month, beating out a 1979 record of -14.5 C.
"That’s a really long stretch. Persistent cold is basically what characterized this winter and especially February," said Environment Canada meteorologist Maxime Desharnais.
Desharnais says it is possible Montreal had an even colder February 115 years ago in 1889, though "blurry data" makes it difficult to prove.
Temperatures were even more extreme elsewhere in Quebec, with records broken in Quebec City and Sherbrooke.
Saguenay ended February with an average of -21.1 C.
Arctic air blockage
Desharnais says the extreme temperatures were caused by an unusual blockage in the upper atmosphere that kept an arctic air mass more or less stationary over the northeast of the continent.
"We had the jet stream blowing just west of Quebec and Ontario, just blowing that northwesterly cold air from the north, and that thing didn’t move for weeks on end," said Desharnais.
Warmer days ahead?
The temperature has not risen above freezing for the entire month of February, and Environment Canada doesn't expect it to climb past 0 C until Wednesday, March 4.
"It’s March, and the atmosphere is warming up. We are going to stay under the average just a little bit, but the extreme cold that we experienced over the past weeks is behind us," said Desharnais.
Environment Canada warns of a potential storm in the Montreal region on Wednesday, with about 5-10 cm of snow expected.
"Even though the cold spells are pretty much done, winter is not over, yet so we could still get a few weather systems on the way," said Desharnais.