I pulled heads on 7.3 ford up prather when it was 109.. wife tried to hold a couple umbrellas to shade us both... but the heat was too much for her. I got used to it, well so I thought..for about an hr... then after one head was off...i called it quits , I was toasted. Dehydrated & sun burnt. Just like that I felt extremely tired and that next day pissing out my *** and laid up drinking water. I used to fair in 104 no problem. Theres a spot between 98-105* that feels the same to me. Higher than that feels like a hot blanket...it zaps the water right out of you and effects you brain. You slow down...fall asleep and you die. It's not like some old western where you fall asleep n hallucinate a nice little dream then wake up...you organs shut down, shock n heart attack.
