Agree with @Sacto Mitch.
Adding my full tonneau helped a lot. Keeping what little heat that dribbles out of the vents in the cabin.
I’ve driven on the highways at 6am to CNC in the winter, where it’s gotten around 38-40 degrees. I put the top up for that. And it’s manageable.
as @Sacto Mitch mentioned it’s the wind from behind that gets you. I like to wear a hoodie.