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READY RECKONER OF INDIANGEOGRAPHY |23|

2. The Hot Weather Season: 3. The Southwest Monsoon Season
Increase of temperature in May over the north-western
Temperature:
plains, the low pressure conditions over there get further
With the apparent northward movement of the sun intensified.
towards the Tropic of Cancer in March, temperatures
By early June, they are powerful enough to attract the
start rising in north India. April, May and June are the trade winds of Southern Hemisphere coming from the
months of summer in north India. In the coastal regions, Indian Ocean. These southeast trade winds cross the

the north-south extent of isotherms parallel to the coast equator and enter the Bay of Bengal and the Arabian Sea.
confirms that temperature does not decrease from north Passing over the equatorial warm currents, they bring
to south rather it increases from the coast to the interior. with them moisture in abundance.
Pressure and Winds: After crossing the equator, they follow a south-westerly
direction. That is why they are known as southwest
The summer months are a period of excessive heat and
monsoons.
falling air pressure in the northern half of the country.
Because of the heating of the subcontinent, the ITCZ The rain in the southwest monsoon season begins
moves northwards occupying a position centred at 25°N abruptly, there by brings down the temperature
in July. substantially. This sudden onset of the moisture-laden
winds associated with violent thunder and lightning, is
A sudden contact between dry and moist air masses give
often termed as the break or burst of the monsoons.
rise to local storms of great intensity associated with
violent winds, torrential rains and hailstorms. The monsoon approaches the landmass in two branches:

(i) The Arabian Sea branch
1. Mango Shower:
Towards the end of summer,there are pre monsoon (ii) The Bay of Bengal branch.
showers common in Kerala and Karnataka locally,they are
Monsoon Winds of the Arabian Sea:
known as mango showers ,since they help in the early
ripening of mangoes The monsoon winds originating over the Arabian Sea
further split into three branches:
2. Blossom Shower:
With this shower coffee flowers blossom in Kerala and (i) Its one branch is obstructed by the Western Ghats.
nearby areas These winds climb the slopes of the Western Ghats
from 900-1200 m. Soon, they become cool, and as a
3. Nor Westers:
result, the windward side of the Sahyadris and
These are dreaded evening thunderstorm in Bengal and Western Coastal Plain receive very heavy rainfall
Assam .Their notorious nature can be understood from ranging between 250 cm and 400 cm.
the local nomenclature of ‘kalbaisakhi. These showers are
useful for tea, jute rice cultivation. In Assam,these storms After crossing the Western Ghats, these winds
are known as Bardolichheerha descend and get heated up. This reduces humidity in
the winds. As a result, these winds cause little
4. Loo:
rainfall east of the Western Ghats. This region of low
Hot, dry and oppressing winds blowing in the northern rainfall is known as the rain-shadow area.
plains from Punjab to Bihar with higher intensity. (orographic)

(ii) Another branch of the Arabian sea monsoon strikes
the coast north of Mumbai. Moving along the
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