Relatively new tube exploded by itself without any external force This morning I heard the tube in the rear tire explode (I never heard a tube explode before. It was quite loud).
I hope someone can shed some light on why this may have happened (and how to prevent it).

Details:


The bike was inside a house and nobody had touched it for 12 hours.
It is a road bike. The tire says pressure should be between 90 and 125 PSI, and just yesterday I inflated it to 110 PSI and after that went for a ride just fine.
The tube was very new, it had only 4-5 days.
The tube has a small hole is one of the sides. The tire has a little crack on that spot. It is very thin and about 0.5cm (0.2 inches) long. The rim seems fine. 
The tire was still in place, it did not come off of the rim.
Two weeks ago it happened with another fairly new tube. That time I didn't hear the explosion, but one morning I found the tire deflated without explanation. Both tubes have the hole in exactly the same place, so I guess the cause is related.
10 minutes before it exploded, I opened a door-window next to it, so the temperature dropped a bit suddenly. However, I'm in California so the temperature is very mild. It's not cold at all.
The bike is in the sun during the day.
A bang explode pretty much only happens when the tube leaks out from tire.   

Either the slit is big enough for the tube to push through or the tire pushed over the rim and the tube leaks out.  Without a tire a tube will only handle a few pounds of pressure. I suspect the tire belt is damaged.  When you see the tire off the rim you might assume the explosion blew the tire off the rim but most likely the tire came off the rim and then the tube exploded.