When to let broody hen set?

[cmitchell]

I have hen who seems to be getting broody. She sits in the next box, puffed out, pecking any hand that goes near her. She will also scream at the top of her lungs if I brave the pecks and collect the eggs under her. I was wondering if it is still too cold to allow her to set on some eggs. I live in Maine and my chickens are housed inside an uninsulated barn.

 

[SarahIrl]

She will incubate the eggs just fine, it's wen the chicks hatch you need to worry about outside temperature. She will try to keep them warm but we all know how independant baby chicks are. Can you set a heat lamp infront of the nest box she will be in?