For cloud development or rain to occur, air must be moved upward from solar heating or terrain features where it is cooled sufficiently to condense (turn to a liquid) around dirt or salt particles in the air. When air flows over land with significant water resources such as the Scandinavian Peninsula, the relatively cooler water tends to cool the air thus encouraging air to move downward. When air moves in a downward motion vice upwards, it is termed stable air. Stable air produces weather such as haze and fog.