I am worried too. I did not go the heat lamp route but maybe that would help with all the humidity. I am hoping with their sleeping coop being nice and dry a good couple of shakes and they should be ok.
We had a couple of days during the winter where it was actually raining then the temperture dropped...same situation...and they were fine. After all the extremes last winter they all kept laying and only stayed inside 2 days that were extremely blustary. No heatlamp, no lights, and no lost chickens except for the rooster's comb. I was amazed but Mother Nature does take care of them. I did take down the feedbags that were providing extra wind blockage a couple of weeks ago.