You'd probably be better off if the internals are oiled instead of greased. In that case, I'd probably avoid one with a coaster brake.
Having said this, I rode my bike with a 7-speed Shimano Nexus hub with a coaster brake and greased internals all over southern Sweden when I lived there, but it rarely goes below freezing there for very long. After the initial adjustment on the probably 20 year old hub, I never touched it again.