is it normal for your heart rate to increase to over 100 bpm during a very hot bath?

Answer 1

Yes. This is very normal and I'll explain why. So when you're taking a hot shower or bath, blood rushes to the extremities (arms, hands, feet) so blood flow is stimulated to the point where your heart rate can elevate to about 90-110 beats per minute to compensate for the volume of blood being pumped in the body. Nothing to worry about!

Answer 2

Why yes, yes it is; that is known as "The Hot Bath Syndrome". 

Answer 3

not normal...........