This morning, my iPhone was really warm and the battery ran down in about four hours.

Any suggestions why? Will I die when it explodes?

What’s your signal like? A network fault would send it mental looking for networks over and over again (I had this, though not the four hours part).

Other option is to reset it and see if it’s just got itself in a tizz

I find it runs really hot if I’m on a long Skype call for example, so as above perhaps it’s struggling for network connection as each re-connection uses quite a lot of power. I would suggest a reboot or at least shutting down all the aps (double click home button etc …)

Double click home button and kill all running apps

Check you don’t have something using GPS – that makes it run pretty hot too.

my HTC one went really hot this morning, I turned off off and on and it seems ok now, not that I know what caused it….

Battery runs down quickly where there’s no signal (such as work) but it doesn’t usually run hot. Turning it off and on again seemed to have solved things and it’s not done it again since. All a bit baffling…

In this weather, what isn’t running hot?
Pity there isn’t a sweaty emoticon.