Batteries work by means of chemical reaction, the colder they are the less the reaction, the hotter the more the reaction (to an extent). Some batteries are better than others in the cold. I've had good luck with alkalines in my car. I live in Maine and we have cold winters.

ditto on alkalines. They have always worked for me and Maryland winters don't compare to Maine's

Put the flashlight on your maintenance plan like your smoke detector. Change the batteries when you change your clocks and use the old ones in something else. It would be very easy to not touch it for a few years and find you have a battery that has leaked and corroded the innards just when you need it.