The flash point of nitro is 109F and boils at 214F while methanol is 61F and 147F. I can't remember ever having a fuel problem even on days well over the 100F mark in the shade but I do remember putting a thermocouple down below the spray bar on one engine at full throttle and there was a temp drop of about 20 degrees. This would have been from a combination of the fuel (mainly the methanol) vapourising and the lower pressure.