Barry,
I'm from Calgary, but my son lives in Fort McMurray, so this is close to home in a manner of speaking.
Flying is a year round activity there and in every part of Canada. If it wasn't, the country would grind to a halt from November to March.
The only difference in winter is that the floatplanes are either beached or on skis and most light aircraft will have cooling baffles installed and lighter weight oil. Any aircraft living outside or in unheated hangars have to be carefully pre-heated.
I've flown a PA-28 when the ground temperature was -25C, but I don't think I would have gone flying, unless I had to, in the cold snap in Fort McMurray earlier this year when it was in the -40 to -50 range. My son said
even the locals who like winter, were starting to complain
I42