Been cleaning at quite hot water on upvc double glazing, had no problems. But turn it down on wooden frames double glazing and single glazing. Not running the risk there. I had my water on barely warm and I could hear the woodwork expand, kind of scary! Wouldn't imagine doing that with hot water.
Reviving my lcd thermometer on the pole idea but making it more sturdy so it doesn't break so easily. That way I at least know what temperature the water is.