This is great info thank you! I don't plan to have a litter until spring due to the small litter size of hollands, but we have such crazy spring weather that I will need all of these skills and tips! Thanks!In the 2014 polar vortex this hutch wasn't built but they did fine in our unheated garage... Which is admittedly a handful of degrees warmer than outside because of radiant heat from the house, and windchill factor is nil.
Litters of 3 or less can't maintain their body temps outdoors in less than 25ish*F. 4 is sketchy and depends on nest quality, moms care (is she a once a day or twice a day feeder? Does she like to pee in the boxes, even just once? Does she clean her kits well?) and general kit quality. Never had a problem with 5+ kits.
Litters born on the wire (in this case, in the hay) or not in a properly built nest may struggle. I keep extra fur around from previous nests of molts and I use it to help moms that don't build good nests build better nests.
As a reminder, a kit isn't dead until it's warm and dead (goes for any baby anything you find, and a lot of adult things too) so if you DO get a chilled litter, don't give up hope. Try to warm them up before you call it.
Never had to bring adults inside for anything but a malfunction in the hutch (like broken wire).