Ha, I just saw this now.... I really can't think of anything. When my friends go out and we notice it's cold, it's usually just goes like,
"Wow, it's pretty cold out now" - Me
"Thanks for stating the obvious!" - Friend #1 (the one who likes to point out all my mistakes)
"Hey! Watch your tone! And put your coat on!" - Friend #2 (the one who acts like a mother all the time)
But for canadian slang? We don't really have one, or if there is one, we don't use it.