Batteries do not like cold weather, that is why most people only find out their car battery is getting weak when the weather turns cold.
They will need more regular charging when it is cold.
remember rubbing the TV control batteries when they were getting flat? You were just warming them to make them more efficient.
On the subject of batteries, I will share a little gem with you all regarding leisure batteries - you can get them for FREE or very cheaply - go to a mobility scooter supplier and blag a couple of old ones, they are generally perfectly servicable but have no second hand value as old people always want new ones! They also cost to dispose of so you will be able to get them for a nominal fee or totally free.
I got 2 a couple of weeks ago, in perfect like new condition complete with the correct charger, for absolutely nothing but my time in asking.