Why does the human body work better at 22 degrees Celsius and not 37?

How hot, or cold we feel depends not only on the actual temperature of the ambient air but also on the relative humidity of that air and on whether it is still or moving. How cold one feels in an air conditioned room depends on how close one is to the vent, and on how the flow of air from the vent is directed. 

When we are outdoor, the "actual" weather temperature may  not be actual even when measured by an outdoor temperature gauge at the airport (location of most weather report temperature gauges) instead of in the yard; we would feel warmer if the sun is shining, and the gauge in the shade would not know that.