Birds have been hatching their eggs outside for generations, but I definitely understand your concern. Is there is a portable shelter you can place over the duck and her eggs?This is my concern also I am new to duck/chicken raising. I found my nest outside our barn on Sept 26th. Worried about them being outside and how much longer will have to wait. I don't want to disturb the nest and my duck is very "squwacky" when she finds me over there. I posted in the thread last night but, no responses yet. I live in southwestern NY state. So anytime now the weather could turn.
The hardest part is being patient. Duck eggs(all but muscovy) are supposed to hatch at 28 days incubation. It is day 29 for mine and they finally piped.