I was in Calgary this time last year - arrived in -17c then two days later it got upto +13c, before plunging back down to -12c. In fact experienced a 20c drop in the space of 8 hours. But the snowfall there is pointless. It rarely accumulates to any depth, and -17c feels nothing like it would it the UK. The rain shadow kills off the chance of any decent snowfall generally. You would expect snow to settle at those low temperatures but it doesn't.