Even a 'low' of 99 degrees is quite sufficient to kill you; how could a local 'regular hiker' not know that? Another thing that didn't make sense is that 'a ranger' advised him to 'use downhill poles' on the hike. The ranger didn't tell him "Don't do it, we rescued somebody who did this last month???" If that's true (and it may not be, perhaps the ranger did warn him) the ranger was quite irresponsible. Believe me, if someone said to me "I'm thinking of hiking down Skyline in July" I would have lots to tell them, but advising them on gear wouldn't be among it 
!!
I agree that this again brings up the issue of 'misplaced confidence'. I almost think that part of it is that we live in such a sedentary society that people who engage in any physical activity at all mistakenly think this equips them for severe athletic endeavors.
