probably not big of a deal. Not that it is a bit cooler outside, my guess is that your metal engine parts have contracted a bit - metal shrinks when its cold. My guess is that a gasket or perhaps your piston rings (if your engine is a bit older) have contracted a bit which means their may be a bit of residual oil in the piston chamber. When you start the car, you burn off that oil in the first few seconds - boom you have a puff of smoke.

My car has different squeaks and rattles this time of year, probably for the same reason.

It would only be an issue for you if the smoke continues long after you start the car. Then you have a real issue.

Just check to make sure you have enough oil in your engine every week or so. I'm sure you'll be fine.