in general my hand will heat up while using the mouse, and the other one like others have said will remain normal temp. although i give off alot of heat anyways so it will be more than normal temp.
Maybe it's an Aussie thing, cause on a cold weekend morning my hand will freeze to death and I have to keep putting my mouse hand in my pocket for a bit to take the chill off it lol...So you ain't the only one!