Incubator needed?

[shroomiChicken]

Should I use a incubator to hatch my hens eggs during weather below 47 degrees or are they fine on their own? Or should I add something to their coop?

 

[Percheron chick]

They will be fine with the hen. I gave a hen store bought chicks in the middle of December in a snow storm and didn't loose one.
Just make sure they are confined to a small area where they can't wander too far away from her and get lost.