I already started supplementing with light. Goes on at 6am in the coop and turns off at 8 pm. Did you add a heat source in the coop?Sure they will. Lots of sun left even if you do not supplement lighting right now. I have had for last 3 fall seasons pullets lay right through winter. I did supplement from end of Oct and all winter with lighting.
My coop is insulated but as you know Canadian winters are very long and cold.