FarmMama, I live in upstate NY, avg temp this winter has been low teens, with many nights below zero. My Seramas have weathered these temps just fine. My BR roo has shown a bit of frost-bite on his comb but the Seramas couldn't care less about the cold. No frost-bite on my Serama roo's comb at all. And they are tiny- fit into my 11 year-olds palm. Alot of people still think because these birds are small, and come from a warm climate, they can't tolerate the cold. That just isn't true. I don't free-range my Seramas, they chose to spend alot (but not all) of their time this winter in the coop, but do go out into the run several times a day. All's I'm saying is if you want them to go out into the coop with the others, don't be afraid to, they aren't nearly as fragile as some people believe.
Ok, I'd better add a disclaimer here, my Serama's share their space with some banty cochins and silkies, when they get cold, they snuggle together. I don't know how well a couple of Serama's would fare on their own in these cold temps we've had this year in an unheated coop.