Is it a cold draft that you feel, indicating a gap in the seal, or is it the effect of the heat in the garage continually being lost to warm a surface whose other side is being chilled by contact with the outside air?

The seal is right up against the garage door when it is closed and I don't see any opening to the outside. It is only one seal. I'm sure the seal could be letting in a little air along with the cold is being transferred thru the vinyl. I have thought about cutting a strip of foam to place up there but I don;t know what would be the best way of attaching it?

You might find a configuration of peel-and-stick foam that you can apply to the top of the door in a way to slow the convection heat loss, but I've alway found it rather futile to try to keep an unheated garage from getting cold.

Thanks, I'll give it a try.