Soaking prior to shed is actually detrimental to a clean, healthy shed. It actually removes the oils that develop between the layers of old and new skin to help separate the two and provide a clean shed. Soaking and wiping with a cloth should only be done after an incomplete shed to aid in removing any stuck pieces, which should never be forced off. And oils can be extremely harmful as well, as stated above. Snakes shouldn't need any help in shedding if the husbandry is correct, but obviously there are exceptions to that rule. I'm in MA where humidity is also a nightmare in winter, and have never had any shedding issues. I have to add a few sponges or some moss to the enclosure, maybe a second water dish and never had any issues. The outside temp for one day will not affect a shed either. The outside temps being cold draws moisture out of the air, and artificial heat completely sucks moisture out of the air, but it would take a lot longer than one nice day to help humidity enough to affect a shed.