There are four seasons:
(a) The cold season or N.E. Monsoon season.
(i) Starts in December and lasts till February.
(ii) There is high pressure over the Northern Plains and low pressure over the ocean.
(iii) Winds blow from land to sea.
(iv) N.E. Monsoons are cold and dry. They do not cause rain in the north but pick up moisture from the Bay of Bengal and cause rainfall in Tamil Nadu.
(v) Temperate cyclones or depressions from the Mediterranean Sea cause rain in Punjab, H.P. and western part of U.P. This rain is beneficial to crops like wheat and barley.
(vi) It is extremely cold in the hills where there is heavy snowfall.
(b) The Hot season.
(i) Starts in March and lasts till May.
(ii) There is low pressure in northern region and high pressure in Deccan which prevents winds from blowing towards north.
(iii) It is mostly dry with high temperatures and local storms like loo, Kalbaisakhi and Mango showers blow in this period.
(iv) It is hot and dry throughout the country except the coastal regions and hills which have a pleasant climate.
(c) The rainy or the S.W. Summer Season.
(i) This season begins in June and lasts till September.
(ii) The low pressure in the north-west becomes strong enough to attract the S.E Trades which enter India as the S.W. Monsoons.
(iii) These divide into two branches due to the triangular shape of India:
– The Arabian Sea Branch.
– The Bay of Bengal Branch.
(iv) The Arabian Sea Branch causes:
– Heavy Relief Rainfall (over 200 cms.) on the western coast and windward slope of Western Ghats, e.g., Panaji.
– The Deccan Plateau receives less than 20 cms. of rain as it lies in the rain shadow area, e.g., Pune.
– Rajasthan does not get much rain as these winds blow parallel to the Aravalli Hills.
(v) The Bay of Bengal Branch picks up moisture from the Bay of Bengal and causes:
– Heavy rain in N.E. India (Cherrapunji gets about 2500 cms. of rainfall. Shillong gets about 250 cms.).
– Rainfall decreases as winds move westwards up the Ganga Plains.
– Rajasthan receives very little rain as it lies in the rain-shadow of the Aravalli Hills.
(d) The Retreating S.W. Monsoon Season:
(i) This season lasts through October and November.
(ii) The sun shines on the Equator in September so the temperature decreases.
(iii) The retreating of the Monsoons means that they become weak and start withdrawing from the country from north to south.
(iv) These winds pick up moisture from the Bay of Bengal and give rainfall to the Coromandel coast.
(v) Tropical Cyclones are common in the Bay of Bengal. They cause widespread damage to life, property and crops.
(vi) The skies are clear, temperatures and humidity is high and the weather becomes oppressive. This is known as ‘October Heat’.