Nope...the bag size limits remain the same.
However, you can simply wear your winter coat when boarding and remove it if you get too warm. It can serve as a "blanket" if needed. If you don't need it in flight and don't want to store it on the dirty floor under the seat in front of you, you can bring a dry cleaning bag to put it in first and them simply stuff it under the seat. Or if there's room in the overhead after everyone has stored their carry-ons, you can place it there.
