I live in California, where it's warm all the time :), but as long as the drums aren't in a damp environment, they should be okay, especially with the fleece lined. Wood will shrink with cold and dry, but it expands when wet, that's the part you want to stay away from. If possible, store them in an attic, it's probably not as cold as outside with the heat escaping from your home through the walls.

I would not store drums that old anywhere but in a dry room that I would be comfortable in without a jacket on.(I live in Canada, I can't leave drums in my garage...).

I know extreme cold can cause pearl covering on vintage drums to shatter. If I were you I would find some space inside!

-Adam

That's correct. they will NOT be okay in freezing temperatures. The wood and the plastic wrap will shrink -but not at the same rate and it could very easily cause cracking at the very least. I wouldn't risk it.