Why did both of my inner tubes blow out on a new bike I've only put 4 hours on?
I have had a couple of times that an inner tube blew up while the bike was parked in bright sunlight. It seems that high temperatures are a contributing factor, but overpressure? I never pump my tires close to the maximum pressure, mostly the pressure is in the lower half of the min-max range. 

The pressure of compressed air increases proportionally to the absolute temperature, i.e. 273+T ;  T in degrees centigrade. Hence an increase from 95F (35°C) to, say, 140F (60°C) will result in an increase by only 8%. I don't believe this itself is causing the blow outs.

More likely the blow outs are due to an undersized inner tube in combination with a high temperature. Rubber is a material that behaves elastically in a limited range. Beyond a point it starts a plastic deformation. I guess that this point drops with higher temperatures. Most inner tubes are specified for a certain width range, e.g. 18&lt;-->23C for road bike clinchers. The remedy is to buy an inner tube that matches closely with the tire width.