Broody runner duck

I noticed one of my ducks didn't come out of the duck house yesterday so today I checked on her and found her sitting on three very warm eggs.  It seems awfully early in the year for her to want to hatch ducklings also she is only about 8 months old. Can a duck successfully hatch eggs this time of year? It's been below freezing at night and I don't have any supplemental heat in the duck house.

Hi Jenn, where in the world do you live and how cold is it likely to be when they hatch?  

I let a broody hen sit on eggs much later into the fall than I thought wise.  Once they hatched I was very glad she was there to mother them.  I'd've been babying them with the heat lamp and worried that they were cold.  She just took them right outside in the 40 degree weather and they tucked under her when they got cold.

I live in the coast range of northern Oregon.  Late Feb early March is usually pretty cold and rainy and our last frost isn't until mid April most years. I just went out to check on her again and she was out foraging with the rest of the flock.