Why does it feel like heat is coming through the floor while driving?

My 1992 Buick Riviera does the same thing. Sorry, I don't have an answer for you regarding this. But I am sure finding that there are so many similarities in each comment that different people are making. I was always thinking.....oh it's in my imagination. Not so. When a person hears 10-15 complaints about the same thing, that says something. Sorry I can't be of help, but I can commiserate.