Droughts are a slow developing and creeping process as against floods, which are quick and rapid.As already mentioned, it is basically the scarcity (or absence) of rains that initiates a drought situation. Long absence or less than normal quantity of rainfall creates a Meteorological Drought, which is forecast on the basis of the forecast of rainfall. But if the rainfall continues to be scanty or totally absent to the extent that there is scarcity of water in rivers, ponds and wells, it is called Hydroiogical Drought.
If the dry conditions make the land parched to the extent that no seeds can be sown, standing crops (if any) wither and there is scarcity of water for irrigation, it is termed as Agricultural Drought and it is forecast by taking into consideration the condition of the crops and soil moisture in addition to the forecast for rain in the coming days.