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The Seasons
- The monsoon type of climate is characterized by a distinct seasonal pattern.
- Temperatures do not vary much along the coast, but rainfall patterns change frequently.
- India has four main seasons: cold weather, hot weather, advancing monsoon, and retreating monsoon .
The Cold Weather Season (Winter)
- The c old weather Season is arrived in India by mid - November and stays till February.
- In Northern India, December and January are the coldest months.
- The temperature decreases from south to north.
- Chennai, which is located on the eastern coast, experienced the average temperature between 24° – 25° Celsius , while in the northern plains , it ranges between 10°C and 15° Celsius.
Characteristics of The Cold Weather Season (Winter)
- Days are warm and nights are cold.
- Frost is common in the north and the higher slopes of the Himalayas experience snowfall.
- The northeast trade winds dominate the country during this season.
- They blow from land to sea, resulting in a dry season for the majority of the country.
- Rainfall occurs on the Tamil Nadu coast from these winds as here they blow from sea to land.
- In the northern part of the country, a feeble high-pressure region develops , with light winds moving outwards from this area.
- These are Influenced by the relief, these winds blow through the Ganga valley from the west and the northwest.
- The weather is normally marked by clear sky, low temperatures, low humidity, and feeble, variable winds
- The inflow of cyclonic disturbances from the west and northwest are a defining feature of the cold weather season over the northern plains.
- These low-pressure systems f orm over the Mediterranean Sea and western Asia before moving into India with the westerly flow.
- They bring much-needed winter rains to the plains and snow to the mountains.
- The total amount of winter rainfall, known locally as' mahawat and is suitable for the cultivation of 'rabi' crops.
- The peninsular region lacks a distinct cold season.
- Because of the sea's moderating influence , there is little seasonal variation in temperature patterns during the winter.
The Hot Weather Season (Summer)
- In India summers occurs due to the a pparent northward movement of the sun , which shifts the Global Heat Belt northward.
- In India, the hot weather season begins in March and lasts till Mid-June .
- In peninsular India , temperatures remain lower due to the moderating influence of the oceans.
- The summer months experience rising temperatures and falling air pressure in the northern part of the country.
- Towards the end of May , an elongated low-pressure area develops i n the region extending from the Thar Desert in the northwest to Patna and Chotanagpur plateau in the east and southeast.
- The 'loo' is a prominent feature of the hot weather season . These are strong, gusty, hot, dry winds that blow across northern and northwest India.
- Dust storms are common in northern India during the month of May.
- These storms provide temporary relief by lowering the temperature and possibly bringing light rain and a cool breeze
- Localised thunderstorms, associated with violent winds, torrential downpours, often accompanied by hail are known as the 'Kaal Baisakhi' in West Bengal.
- Pre-monsoon showers are common near the end of the summer season , especially in Kerala and Karnataka.
- Pre-monsoon showers help in the early ripening of mangoes and thus, it is commonly known as mango showers. '
Advancing Monsoon (The Rainy Season)
- The Advancing Monsoon in India is prevalen t from June to September.
- By early June , the low-pressure area over the Northern Plains has intensified and is attracting trade winds.
- These trade winds originate in the Southern Hemisphere over the warm tropical ocean.
- After crossing the equator, these blow in the direction of the peninsula as the South-West monsoon.
- They cover the entire subcontinent, with the exception of the extreme northwest, in just over a month.
- The windward side of the Western Ghats receives more than 250 cm of rain.
- The northeastern part of the country receives the most rainfall during this season.
- Mawsynram, in the southern ranges of the Khasi Hills, has the world's highest average rainfall.
Phenomenon of Rainfall Break
- Monsoon has its tendency to have ‘breaks’ in rainfall.
- They are separated by rainless intervals .
- These monsoon breaks are caused by the movement of the monsoon trough .
- When the a xis of the monsoon trough passes over the plain s , rainfall is abundant.
- When the axis shifts closer to the Himalayas , the plains experience longer dry spells and widespread rainfalls in the mountainous catchment areas of the rivers.
Destruction caused during the Monsoon season
- These heavy rains cause devastating floods in the plains , causing loss of life and property.
- The amount and duration of monsoon rains are also determined by the frequency and intensity of tropical depressions.
- The monsoon is known for its unpredictability.
- The intensity, frequency, and duration of the dry-wet cycle vary
- While it causes heavy flooding in one area ( Assam, Bihar, Kerala, West Bengal, etc).
- Lack of monsoon causes droughts in other states (Rajasthan)
- Its arrival and departure are frequently erratic.
- As a result, it occasionally disrupts the farming schedules of millions of farmers across the country.
Retreating/Post Monsoons (The Transition Season)
- During October and November , the monsoon trough or low-pressure trough over the northern plains weakens due to the apparent movement of the sun to the south.
- The s outhwest monsoon winds begin to weaken and withdraw gradually.
- By the beginning of October, the monsoon withdraws from the Northern Plains.
- The months of October and November mark the transition from the hot rainy season to the dry winter conditions.
- Clear skies and a rise in temperature signal the end of the monsoon. While the days are hot, the nights are cool and pleasant.
- Northern India experiences a r apid drop in temperature in the second half of October.
