Jester, extremely rich will also result in colder engine temps, remember.
But I don't know by how much, I admit.

Let's elaborate on the question a little bit and ask: "Just what IS standard operating temp of the cylinder head?"
Then consider the difference between 80 deg outside air and 20 deg outside air.
What percentage difference is the delta T?

I don't know the answers, I'm just asking out loud.