Well, if you can touch the area and have to remove your own hand in pain, I would consider that dangerous....
I think it's a little dangerous before that. The human body temperature is around 98.6F and the python feels comfortable around 86 when they're not digesting (a little warmer if they are... around the low 90s). They can tolerate temperatures up to a 100 for short periods. This is why it is so important to give them a gradient so they can regulate on their own.