I would leave them out for the day and bring them in tonight if they are uncomfortable. Outside should be your new standard. They should be outside unless there is a reason for them not to be. They will do great all day today. If they aren't used to the cold still, I would bring them in maybe at your bedtime, not theirs. Let them feel them natural progression of the heat of the day to darkness and get a taste of colder temperatures. When you go to retrieve them tonight, they'll have made a big step toward dealing with the cold themselves. I'm sure they'll appreciate going inside, but I think you'll find they are more comfortable than you imagined outdoors.