AlecMyrddyn pretty well covered it. In mesh gear, sweat evaporates RFN, so you don't get any of the cooling from it, and the hot wind can cook you. There is a good thread on this somewhere, and it does allude to textile not protecting you from motor heat, but I think that's a minor issue compared to convective heating in high temps.
Wet Tshrt and one of those soak/cool bandanna things can keep you more comfortable and safer.
John Moses Browning was God's right hand, inventing the perfect weapon.
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Sometimes the light to see your way forward is provided by the bridge burning behind you.