I know that a lot of the people who feed FF just keep feeding it through the winter. I decided to feed dry because it gets so cold here. January through February the daily high is usully around 20 below. I just didn't want to be thawing out blocks of FF a few times a day.
They should eat what they need in 10-30 minutes. That should not be long enough to freeze unless you get into the deep negatives and stay there. If that's how it was where I lived, I'd use heated dog bowls or figure out something else {like sock warmer type stuff or a microwave heating pack that they can't get to, etc.}