Heat, Humidity and their Effect on Power

I am sure most of you have noticed a loss in engine performance on very hot, humid days. Why is that? Both higher heat and humidity will reduce the amount of oxygen in the air that the engine ingests. Hotter air temperatures thru reduced air density and higher humidity thru the water vapor displacing oxygen. As an engine uses oxygen combined with vaporized fuel in the combustion process there will be less heat is produced in the combustion chamber there creating less cylinder pressure. Less pressure equals less push on the pistons which equated to less power at the wheels.