The detrimental effects of meteorological phenomenon such as wind shear, thunderstorm, ice/snow etc, to aviation safety are relatively well known. But aerodynamic influences due to heavy rain are still the on-going research subject. This paper first reviewed some research finding of heavy rain effects on aerodynamic performance degradation. Then a computational method to compute the two-dimensional heavy rain condition is introduced and the effects of droplet cratering, liquid water content, droplet terminal velocity, air density modification are included. It is felt that the quantitative information gained in this work could be useful to the operational airline industry, and greater effort should put in this direction to further improve aviation safety.