On frosty mornings I turn mine right down,. its 20 - 25 degs Celsius at the brush head depending on how much hose is out,.. lukewarm to the touch, but defo below body temp. Still much better than using cold.
Once its not frosty, I'd go 40 degrees, up to 60 degrees or so on a nice warm day. I haven't cracked a single window yet and I've been hot almost a year.