froid de canard

Bitterly cold winter weather

The sort of bitter cold that has everyone complaining the moment they step outside.

Couvre-toi bien, il fait un froid de canard ce matin.

Wrap up warm, it's absolutely freezing this morning.

First turns up in print in 1887, in a journal already asking readers where it came from. The favourite theories all involve duck hunting: some reckon the cold is what makes it good hunting weather, others that it's short for cold enough to freeze a duck's feet solid.