Hatching in Winter?

[Daneduck]

I was reading through the post and replies, so I believe I have found my answer. I'm still kinda a new duck mom, so please forgive my ignorance while I try to learn. I have hatched my duck eggs last spring. I had someone want to hatch some of my eggs, so I said no problem. Now I'm wondering if the eggs are even fertile, since we haven't reached temperatures over 25*F in weeks and the duck house isn't heated. What are the chances?