Keep RC Lipo batteries warm (room temp) and/or next to your body while outside in cold weather.
Once you start using them, they’ll heat internally to some extent and ‘can usually avoid cold temperature induced voltage sag.
As far as what temps for RC Lipo packs/bricks. Anything below 50F you’ll be able to notice. 30F and below will become severely compromised and 15F pretty much forget it.
But, start with ‘em warm and they should be okay for at least several minutes. Depends how cold it is outside...