Is it normal for the iPhone 5S heating up especially when surfing the net on Wi-Fi? In normal mode or usage without wifi, no heat up. Only when surfing the web on my home wifi. The battery life remains fairly normal lasting around 5 days (or even more) when not on wifi mode. Only back part heats up. Its quite warm. For those of you owning an iPhone 5S running iOS 8.1.2 do you guys notice any heating up issues? Thanks!