Season of India

• Changes are particularly noticeable in the interior parts of the country.
• coastal areas do not experience much variation in temperature though there is variation in rainfall pattern.

The Cold Weather Season (Winter)

• Mid-November in northern India and stays till February. December and January are the coldest months in the northern part of India. sun shines vertically over the Tropic of Capricorn
• Temperature decreases from south to the north.
• Temperature of Chennai (24° – 25° C) & Northern plains (below 21° C [Night - freezing point in Punjab and Rajasthan]).
• Days are warm and nights are cold.
• Frost common in North & Snowfall in higher slopes of the Himalayas.
• cold winds coming from the Caspian Sea and Turkmenistan bring cold wave along with frost and fog over the northwestern parts of India.
• Northeast trade winds prevail over the country. They blow from land to sea and hence, most part dry season.
• Rainfall occur in TN coast; wind blow sea to land.
• winds blow through the Ganga valley from the west and the northwest.
• clear sky, low temperatures and low humidity and feeble, variable winds.
• Inflow of cyclonic disturbances from the west and the northwest, low-pressure systems, originate over the Mediterranean Sea and western Asia and move into India along with westerly flow. (weak temperate cyclones from the Mediterranean Sea cause rainfall in Punjab, Haryana, Delhi and western Uttar Pradesh).
• winds start blowing from northwestern high pressure zone to the low air pressure zone over the Indian Ocean.
• Rains over the plains and snowfall in the mountains.
• Winter rainfall locally known as ‘mahawat’. Cultivation of ‘rabi’ crops.
• Peninsular region seasonal change in temperature pattern during winters due to the moderating influence of the sea.

The Hot Weather Season (Summer)

• Northward movement of the sun. heat belt shifts northwards. sun towards the Tropic of Cancer in March. March to May.
• In March, 38° Celsius, on Deccan plateau.
• In April, Gujarat and Madhya Pradesh - 42° Celsius.
• In May, 45° Celsius is common in the northwestern parts of the country.
• Peninsular India, temperatures remain lower due to the moderating influence of the oceans. Western Ghats remain below 25°C.
• Rising temperature and falling air pressure. low-pressure (ITCZ) moves northwards occupying a position from the Thar Desert in the northwest to Patna and Chotanagpur plateau in the east and southeast.
• Easterly or south easterly over north Bengal and Bihar.
• southwesterly monsoon is in reality ‘displaced’ equatorial westerlies.
• heart of the ITCZ in the northwest, the dry and hot weather season is the ‘loo’. Blowing during the day over the north and northwestern India.
• Local Storms - Sudden contact between dry and moist air masses gives rise to local storms of great intensity.
• Direct exposure to these winds may even prove to be fatal. Dust storms in May in northern India.
• Storms bring temporary relief as they lower the temperature and may bring light rain and cool breeze. West Bengal, these storms are known as the ‘Kaal Baisakhi’.
• Close of summer season, pre-monsoon showers are common especially,
• “Mango Shower” - end of summer, there are pre-monsoon showers in Kerala and costal area of Karnataka.
• “Blossom Shower”- coffee flowers blossom in Kerala.
• “Nor Westers” - evening thunderstorms in Bengal and Assam. Kalbaisakhi’, a calamity of the month of Baisakh. useful for tea, jute and rice cultivation. Assam, these storms are known as “Bardoli Chheerha”
• “Loo” - Hot, dry and oppressing winds blowing in the Northern plains.

Summer - December to Febuary

Winter - June-July

Advancing Monsoon (The Rainy Season/ South West Monsoon)

• July, low-pressure condition over the northern plains. attracts, the trade winds of the southern hemisphere
• south-east trade winds originate over the warm subtropical areas of the southern oceans. cross the equator and blow in a south westerly direction (Bay of Bengal and the Arabian Sea) entering the Indian peninsula as the south-west monsoon.
• Winds associated with violent thunder and lightening.
• Exception of the extreme north-west, the monsoon winds cover the country in about a month.
• Windward side of the Western Ghats receives very heavy rainfall, more than 250 cm. Deccan Plateau and parts of Madhya Pradesh also receive some amount of rain. Max Rainfall – North East (Mawsynram in the southern ranges of the Khasi Hills receives the highest average rainfall in the world).
• Ganga valley – Rainfall decrease east to west.
• Rajasthan and parts of Gujarat - scanty rainfall.
• Breaks in monsoon (Rainless Interval) are related to the movement of the monsoon trough (trough and its axis keep on moving northward or southward).
• Trough in plain – Rainfall is good. If closer to Himalayas - longer dry spells in the plains. widespread rain occurs in the mountainous catchment areas of the Himalayan rivers bring wake, devastating floods causing damage to life and property in the plains.
• Frequency and intensity of tropical depressions too, determine the amount and duration of monsoon rains. depressions form at the head of the Bay of Bengal and cross over to the mainland.
• ‘Monsoon trough of low pressure’ known as uncertainties.
• Heavy floods in one part, it may be responsible for droughts in the other.

Monsoon Winds of the Arabian Sea

Split into three branches

1. Western Ghats.
• Windward side of the Sahyadris and Western Coastal Plain rainfall 250 cm & 400 cm
• little rainfall east of the Western Ghats - Rain-shadow area.
2. Coast north of Mumbai.
• Along the Narmada and Tapi river valleys.
• Chotanagpur plateau gets 15 cm rainfall.
3. Saurashtra Peninsula and the Kachchh
• Rajasthan and along the Aravalis - scanty rainfall, too joins the Bay of Bengal branch cause rains in the western Himalayas.

Monsoon Winds of the Bay of Bengal

• Coast of Myanmar and part of southeast Bangladesh. coast of Myanmar deflects a big portion of this branch towards the Indian subcontinent.
• branch splits into two under the influence of the Himalayas and the thermal low is northwest India.
• one branch moves westward along the Ganga plains reaching as far as the Punjab plains.
• other branch moves up the Brahmaputra valley in the north and the northeast, causing widespread rain.
• sub-branch strikes the Garo and Khasi hills of Meghalaya. Mawsynram, located on the crest of Khasi hills, receives the highest average annual rainfall in the world.
• Tamilnadu Remain Dry – Parallel to Bay of Bengal branch, Rain shawdow area of Arabian sea.

Characteristics of Monsoonal Rainfall

• Between June and September.
• Largely governed by relief or topography. windward side of the Western Ghats register a rainfall of over 250 cm.
• Kolkata receives 119 cm, Patna 105 cm, Allahabad 76 cm and Delhi 56 cm.
• Breaks in rainfall are related to the cyclonic depressions. formed at the head of the Bay of Bengal.
• Run off and soil erosion.
• Three-fourths of the total rain.
• Spatial distribution is also uneven. 12 cm to more than 250 cm.
• delayed over the whole or a part of the country.
• earlier than usual, causing great damage to standing crops and making the sowing of winter crops difficult.

Retreating/Post Monsoons (The Transition Season/Northeast Monsoon)

• October - November, Movement of the sun towards the south. low-pressure trough over the northern plains becomes weaker gradually replaced by high pressure.
• Beginning of October, monsoon withdraws from the Northern Plains.
• October - November, period of transition from hot rainy season to dry winter conditions.
• Day temperatures are high, nights are cool. Land is still moist.
• conditions of high temperature and humidity during day - ‘October heat’
• In November move over karnataka & Tamil Nadu.
• Middle of December, the centre of low pressure is completely removed from the Peninsula.
• Cyclones generally originate over the Andaman sea & cross the eastern coasts of India cause heavy and widespread rain, very destructive, deltas of the Godavari, the Krishna and the Kaveri are frequently struck by cyclones.
• Sometimes, these cyclones arrive at the coasts of Odisha, West Bengal, Bangladesh & Myanmar.
• Bulk of the rainfall of the Coromandel Coast is derived from depressions and cyclones.

Traditional Indian Season

Seasons	Month  (According to Indian Calendar)	Month (According to Gregorian Calendar)
Vasanta	Chaitra-Vaisakha	March - April
Grishma	Jyaistha-Asadha	May – June
Varsha	Sravana-Bhadra	July – August
Sharada	Asvina-Kartika	September – October
Hemanta	Margashirsa-Pausa	November – December
Shishira	Magha-Phalguna	January – February