India enjoys variety of seasons due to geographical locations. There are four seasons:
- Cold weather season (December - February)
- Hot weather season (March - May)
- Advancing South-West monsoon season (June - September)
- Post or retreating monsoon season (October - November)
1. Cold Weather Season
The duration of cold weather season is from December to February. The temperature decreases from the South to the North. December and January are the coldest months and the average temperature in North is (12° to 15°C) and in South (25°C).
Frost is common in the North and North-West India. There is light rainfall in this region due to Western disturbances. Higher slopes of the Himalayas experience snowfall. During the winter season, North-East trade winds prevail over India. They blow from land to sea. Hence, for most part of the country, it is a dry season.
However, the Tamil Nadu coast receives winter rainfall due to these winds. A part of North-East trade winds blow over Bay of Bengal. They gather moisture which causes rainfall in the coastal Tamil Nadu while the rest of the country remains dry. In the northern part of the country the weather is marked by clear sky, low temperatures and low humidity. The winter rainfall is very important for the cultivation of ‘Rabi’ crops.
2. Hot Weather Season
By the end of February the temperature starts rising. So from March to May it is hot weather season. There is high temperature in plains, western part of India and in the central part of peninsular India. In Northern plains, an elongated low pressure which is called monsoonal trough is created, which extends from Jaisalmer in western Rajasthan to Jharkhand and parts of Odisha to the East.
However, over Indian Ocean south of the equator high pressure belt begins to develop in this season. In North-West India, afternoon dust storms are common. During summer, very hot and dry winds blow over North Indian plains. They are locally called ‘Loo’. Exposure to these hot winds may cause heat or sun stroke.
This is also the season for localised thunderstorms, associated with violent winds, torrential downpours, often accompanied by hail. In West Bengal, these storms are known as the ‘Kaal Baisakhi’ (calamity for the month of Baisakh). Towards the close of the summer season, pre-monsoon showers are common, especially in Kerala and Karnataka. They help in the early ripening of mangoes, and are often referred to as ‘mango showers’.
3. Advancing South West Monsoon Season
After the scorching heat of summer season people eagerly wait for the rains which can give them relief. Farmers wait for the rains so that they can prepare their fields for the next cropping season Kharif. June to September are the months of advancing South-West monsoon season.
By the end of May the monsoon trough further intensifies over north India due to high temperature in the region. The General direction of the wind during this season is from South-West to north-east. These winds are strong and blow at an average velocity of 30 km per hour. These moisture laden winds first hit at Andaman and Nicobar Islands in the last week of May and Kerala coast in the first week of June with violent thunder and lightning.
This South-West monsoon that flows in to India brings about a major change in its weather. Two branches of south-west monsoon originate from:
- Arabian Sea
- Bay of Bengal
The Arabian Sea Branch obstructed by Western Ghats gives heavy rainfall on the Western side of Western Ghats. It reaches Mumbai by 10th June. When this branch crosses the Western Ghats and reaches the Deccan Plateau and parts of Madhya Pradesh, it gives less rainfall as it is a rain shadow region. Further, this branch reaches in Northern Plain by 20th June.
The monsoon winds that move from Bay of Bengal strike Andaman and Nicobar islands North-Eastern states and coastal areas of West Bengal and covers the whole of India by the 15th of July. They cause heavy rainfall in the region. However, quantity of rainfall decreases as they move towards West over the Northern plains.
For examples rainfall at Kolkata is 120 cm, Allahabad 91 cm and Delhi 56 cm. The monsoon tends to have ‘breaks’ in its rainfall which causes wet and dry spells. This means that monsoon rains occur only a few days at a time. As the monsoon comes after the hot and dry summer season, the rainfall brings down the temperature.
This decline is from 5°C to 8°C between mid June and mid July. This is the time when many parts of India face floods also. This is mainly because of heavy rainfall and inability to manage water resources more systematically. On the other hand there are many areas that experience drought conditions during this season.
4. Retreating or Post Monsoon Season
October and November are the months of post (or retreating) monsoon season. The temperatures during September-October start decreasing in north India. Monsoonal trough also becomes weak over North-West India. This is gradually replaced by a high pressure system.
The South-West monsoon winds weaken and start withdrawing gradually from North Indian Plains by November. In October the weather remains humid and warm due to continuing high temperature and moist land in month of October.
In Northern plains hot and humid weather becomes oppressive at this time. It is commonly called ‘October Heat’. However, towards the end of October, temperature starts decreasing, making nights pleasant.
This is also the time of cyclonic storms which develop in the Bay of Bengal as the low pressure of North India shifts to this area. These storms create havoc in coastal areas of Odisha, Andhra Pradesh and Tamil Nadu, especially in the deltas of Mahanadi, Godavari and Krishna rivers.