How cold does it get in winter?

Question

We all know that The North of Westeros is already pretty chilly even in summer, with it only getting colder and colder when you go beyond the wall.

However, winters are meant to be significantly colder, not just for the North but presumably for the entire world.

How much are other, non-Northern places (such as Kings Landing, Dorne, and Essos, which have been depicted as warmer) affected by Winter? Do they face the same issues that the North faces (risks of freezing to death or starvation), or do they not have to worry about it as much as the Starks?

Answer 1

Well, in the Epilogue of ADWD it is

Snowing heavily in King's Landing and a white raven arrives from the Citadel indicating that winter has come

So it can at least get below freezing in that part of Westeros.

There are some more details in this answer, in particular:

Mr Martin, why does Westeros seem the only place effected by the Others and the long winters? The other parts of the world seem not to care.

George_RR_Martin - Westeros is not the only place affected, but it's affected most strongly, because it's the only landmass that extends that far north. The other continent is bounded to the north by an icy polar sea.

Which seems to indicate that places further north are affected more by Winter.