SOLVED. Post apocalyptic world where poor are branded and mine coal. Spoilers ahead. [s]

[Holly]

I read a book in high school (2004 ish) about a post apocalyptic world where the poor are branded and mine coal (I think) and it's always cold due to the sun being covered by smoke from coal fires. The main character is supposed to be branded but something happens I don't quite remember, and she ends up a servent for someone upper class. She learns that if she thinks about being warm she can stay warm and because of her position in society she's able to teach this to enough people that they are able to reduce the coal use and it clears the air.
It's a much better read (from what I remember) than I'm making it sound but any help would be appreciated.

[Rosa]

Winter of Fire?

[Holly]

yes!!!! thank you!

[Jamie]

Gah! Beat me to it! I knew immediately from the headline. It's can be tricky to find, since it was out of print for a while (just re-released in paperback for the 25th anniversary).

[Rosa]

You're very welcome, Holly!
I know how frustrating that is, Jamie. It's happened to me many a time.