The process of condensation can only begin at this point. When air is cooled below this point, the air becomes oversaturated and precipitation results. Condensation and precipitation thus can only occur as a result of cooling of air. The main natural way by which air cooling occurs is through the rising of air. Convectional activity primarily occurs in the tropics throughout the year and in the summer season in the middle latitudes.
Orographic activity occurs wherever mountains block prevailing air.
Frontal or cyclonic activity primarily occurs in the middle latitudes, especially in the winter but also commonly in the summer. Tropical air masses originate in the lower latitudes and are therefore generally warm. Polar air masses originate in the higher latitudes and are therefore generally cold. Continental air masses originate over land and are therefore generally dry. Maritime air masses originate over water and are therefore generally wet.