Clouds develop under various atmospheric conditions and aerosol size distributions which governs rain processes in clouds. Using a 2000bin cloud model it was possible perform a highly detailed examine of rain formation processes in clouds. The model allows us to determine the effect of changes in both thermodynamic conditions and aerosol size distribution on rain formation processes. Thermodynamic conditions governs cloud evolution time: a more stable thermodynamic conditions, slower updraft generated within the cloud and evolution time is longer, hence rain processes can be completed within the cloud lifetime. In contrariety, an unstable thermodynamic conditions, faster updraft generated, and clouds develop in a shorter time, hence some rain processes will not be completed by the cloud life time or in extreme cases, will not even start. Changes in aerosol size distribution may shorten or prolong the time needed for clouds processes to be initiated in the clouds. An artificial change in aerosol size distribution may result in transforming a non productive rain process to a productive process and via versa, while even this change can be maximized using an aerosol of specific size.