(i) The Indian monsoon has wet and dry spells. The monsoon rains take
place only for a few days, at a time. They are interspersed with rainless
intervals.
(ii) These breaks in monsoon are related to the movement of the monsoon
trough.
(iii) The trough and its axis keeps on moving northward or southward which
determines the distribution of rainfall.
(iv) When the axis of the monsoon trough lies over the plains, rainfall is
good in these parts.
(v) on the other hand, whenever the axis shifts closer to the Himalayas,
there are longer dry spells in the plains and widespread rains in the
mountains catchment areas of the Himalayan rivers.
(vi) These heavy rains bring devastating floods that cause damage to life and
property in the plains.