I’ve never felt any appreciable heat that made me have a second thought. I can’t imagine even in a water resistant case it’s that big a deal compared to the multi core snap dragon processors with high def graphics,cell tx/rx, gps, etc that a Samsung phones are capable of doing on a daily basis. That being said I’m not a thermal or RF engineer...just a techie that hasn’t felt the temp of his own radio as ever being alarming.