Our ducklings had their first 2°C (35F) night outside and they are doing fine. Ok, they have a heat-pad and an infrared lamp but this morning they were waiting outside of their cave for me to bring their water. Your weather should be much warmer than ours here, you're on the sea-side of the Appalachians. I'm a bit worried about next week, the forecast says -10°C (14F) for Wednesday night - i may wrap some movers blankets around the duckling house.
We are right up next to the mountains and it gets really cold - I'm over it and ready for Spring! Yeah we're supposed to get down to 14F also - not looking forward to it at all. I mean gosh it was 60 last week! Blankets around that duck house sound good - electric heated blankets sound better LOL!