Paul, you've just answered a question that I had. When the thermostat reached 32 degrees, it would flip over to -31 degrees. That would be the overflow of which you speak. With that change to a long, I'm happily reading 69 degrees. The sensor has a range up to 100,and can read up to 99, which is a range of 100.
Wildbill, thanks for the suggestions, I've put them in place. I'm still pretty new to programming, so they were quite valuable tips. The suggestion about tempc == right vs. tempc < too_hot was particularly good, I hadn't even thought of that.