We are minus 2.2 degrees here in MI and my banty cochin is trying to hatch a bunch of eggs. She did the same thing last winter. She hatched 13 chicks and all made it through the winter with no help from me. I did put a heat lamp out there for them but the hen chose not to use it. Am I worried? No. She is experienced and a good ma hen. I figure they know what they are doing. If your hen is a first time ma to be, you may want to keep a good eye on her. Are all the eggs suppose to hatch at the same time? If not, you may want to take the first chicks that hatch away while the hen finishes hatching the rest. When all eggs are hatched you can put the other babies back. Good luck and have fun.
I have a few broody Silkies - this is my first year with Silkies and I knew they had a tendency to go broody, but I didn't realize HOW broody they are. So far they've done great. First timers hatched their eggs and raised their babies with no help from me - no heat lamp at all, but it's only gone into the teens here. A few more are due to hatch soon - silly me forgot to write the date down