Pavel, from what you describe the motor was too rich for the hot day...what was causing your flameouts out of the pits can be caused if the tank is filled all the way to the rim of the tank and when the lid snaps shut it forces extra fuel into the motor that all ready a little rich from the tune...this causes the car to splutter away from the pit, most of the time it will clear its self but if the excess fuel puts out the glow of the plug the motor will cut out.
also as matt said a rich lsn and too wider idle gap can add to it going rich out of the pits.