It could be leaf scorch combined with some iron chlorosis. Some tree species in Utah get yellow leaves due to high soil pH. When that happens there isn't enough chlorophyll in the yellow areas and sunlight can "sunburn" those areas. That could be what happened in the brown areas. However, chlorosis is unusual in English oak. If it is chlorosis many other plant species should be yellow (in summer) in your area. There is nothing else that comes to mind.

Also, it is only on the south side of the trees.  Does that make scorch more likely?

The S, SW, and W sides of the tree would show it the most because those sides of the tree are exposed to the most heat.