#1 Adjust for more boil off -- it boils off more due to the larger temp difference, and the fact that cold, winter air is usually dry.
#2 Here's what not to do:
Have a massive boil over, because you went inside for something and then hung out in there a little too long, leaving wet stuff everywhere.
When it's cold, that freezes.
Then, do not decide, that because it is cold you are going to pour your kettle out instead of siphon.
Because when you pick up that 5 gallons of boiling hot wort, and you spin around with it in your hands, on ice, things can get a little dicey.
I regained my balance, but I needed a beer afterwards.
I was home alone, and the thought of slipping on the ice, covering myself in boiling wort while falling down, and then passing out while lying in the wort while it cools and freezes to me would be a bad way to go...
Other than that, brew on my friend!