I live in Montana and winter came early for us this year. There are a few things I do a little differently in winter. The main one, aside from wearing more layers to stay warm, is I bring my driving bridles and driving lines in the house and store them inside. Then I harness my pony and at the last minute, before I hitch to the cart, I grab the nice warm bridle from the house and put it on him. This way the bit isn’t cold!
Before I started bringing it inside I would put the entire bridle in my coat to warm the bit before putting it on. If you tuck the bit into your armpit, it will warm a little faster.
There are also bit warmers you can buy. They will either need to be warmed in a microwave before putting them on your bit or some of them only require a hand warmer to help them warm the bit.
Just one of the things we have to think about when we live in cold climates. No horse likes having an ice cold piece of metal put in their mouth!