(i) The monsoon rains take place only for a few days at a time. They are interspersed with rainless intervals. The breaks in monsoon are related to the movement of the monsoon trough. When the axis of the monsoon trough lies over the plains, rainfall is good in these parts. 

(ii) On the other hand, whenever the axis shifts closer to the Himalayas, there are longer dry spells in the plains, and widespread rain occur in the mountainous catchment areas of the Himalayan rivers. These heavy rains bring in their wake, devastating floods causing damage to life and property in the plains. The frequency and intensity of tropical depressions too, determine the amount and duration of monsoon rains. 

(iii) The monsoon is known for its uncertainties. These are untimely, irregular, unpredictable and unevenly distributed. The alternations of dry and wet spells vary in intensity, frequency and duration. While it causes heavy floods one part, it may be responsible for droughts in the other. It is often irregular in its arrival and its retreat. Hence, it sometimes disturbs the farming schedule of millions of farmers all over the country.