Here are some recommendations that I sent my individual coached athletes today. That said, if you are drinking almost 2 bottles per hour, I highly recommend in this heat that you limit water. 50% is dangerous unless you are adding in salt tablets or other sources of electrolytes. Your body must have electrolytes to absorb any fluids you intake including water. Electrolytes are your friend especially if you have low blood pressure and/or heavy sweat rates.
And here are my recommendations for training in extreme heat.