The Indian Meteorological Department recognises four seasons, viz.:

1. Winter (December-March)
2. Summer (April-May)
3. Monsoon (June-September)
4. Season of retreating south-west monsoon (October - November)

India situated in Northern hemisphere, the tropic of cancer passes through the middle part of the country.
As a result, the southern half of the country has a tropical climate.
During winter the northern half of the country is warmer than areas of similar latitudinal location by 3°to 8° Celsius.
Owing to the large expanse of the country, its interior parts become very hot during summer.

The Southern part of the country is influenced by the sea (Arabian, Bay of Bengal and Indian Ocean)
The Tropical monsoon type climate of the country is influenced by

1. Latitude
2. Nearness to the sea
3. Altitude
4. Direction of prevailing winds
5. Direction of mountain ranges
6. Character of soil

The annual rainfall of India is 120 cm, a slightly more than the global mean of 99 cm.
The highest normal annual rainfall (1187 cm) in the world has been recorded in Mawsynram (Meghalaya) while the western part of Jaisalmer district (Rajasthan) is one of the driest part of the world recording about 9 cm of rainfall in a year.
Depending upon the total annual rainfall, the country can be divided into five major regions.

1. Region of Very Low rainfall - (less than 30 cm in a year)
2. Region of Low Rainfall - (30 to 60 cm in a year)
3. Region of Medium Rainfall - (60 to 100 cm in a year)
4. Region of High Rainfall - (100 to 200 cm in a year)
5. Region of Very High Rainfall -(about 200 cm a year)

India has varied temperatures.
While Darjeeling and Simla have the lowest temperatures between 15.7°C and 16.9°C, Nagpur registers 35.5°C.
Rainfall is erratic.
Areas like West Coast, Bengal, Assam, etc. get the heaviest rain of above 200 cm annually.
Mumbai, Madhya Pradesh, Bihar, etc. receive 100 to 200 cm and Chennai, North Western Deccan and upper Gangetic Plain have 50 to 100 cm.

The Thar Desert receives only 10 cm of rainfall.
While the rainy season in most parts of the country is from June to September, in Tamilnadu & Andhra Pradesh, it is during October-December.
The temperature in the south seldom drops below 20°C.
The southeast gets most of its rain between October and December and by March, temperature rises throughout the country.
In June, 38°C - 43°C is common in the north.

The lowest average temperature is 13°C in the Himalayan hill stations of Darjeeling and Simla.
Mumbai on the west coast has an annual mean temperature of 28°C and Chennai a mean temperature of 29°C.

The Trans-Himalayan and Greater-Himalayan regions.
Dras and Kargil of Ladakh region are the coldest regions in the country where temperature falls below -40°C.
In west Rajasthan at Barmer where temperature shoots upto 50°C (122°F) during daytime.
This is due to its distance from the sea, absence of rainfall and dry and sandy soil which gets heated up.
Rajkot in Gujarat averages a temperature of 33°C.

Cherrapunji in Meghalaya is the wettest place in India.
ln fact, Mawsynram, 10 km from Cherrapunji receives maximum amount of rainfall in the world- as high as 1080 cm.
It is due to its funnel-shaped location surrounded by the Khasi, Garo and Jaintia hills.
Jaisalmer in western Rajasthan is the driest place which receives the lowest rainfall (less than 10 cm).
It is due to its distance from the monsoon the Bay of Bengal and location in the sub-tropical high pressure belts.

India gets rains by South West Monsoon and North East Monsoon.
The South West Monsoon brings more rain.
North East Monsoon is shorter in duration and comes after South West Monsoon.
Tamilnadu & Andhra Pradesh receives heavy rain due to North East Monsoon only, The South West Monsoon starts in May/June and North East Monsoon starts in November/October.

The south-west monsoon contributes 86% of the total rain in India.
Opens on the West coast around beginning of June and continues till September.
The summer rain has a declining trend as it moves inland.
The first rain decreases westwards in the northern plains giving an average rainfall of:

• Kolkata 119 cm
• Patna 105 cm
• Allahabad 76 cm
• Delhi 56 cm

The north-east monsoon is comparatively a minor monsoon confined to a smaller area of the country particularly the east coast.
This is also called Winter Monsoon and it is Tamil Nadu's major monsoon giving about 45 cm of rainfall in November/December as compared to 38 cm in the four months of the summer.
During the hot summer the land mass absorbs a great amount of heat causing the temperature to rise, thereby creating excessive low pressure.
It causes winds (monsoon) to blow towards India from the seas which have a comparatively high pressure and being moisture-laden being rainfall to the hilly areas of the country.

Assam, Arunachal Pradesh, Meghalaya, Sikkim and northern part of West Bengal -being hilly and in the direct path of the Monsoon winds blowing in from the Bay of Bengal.
The Western Ghats-Rain-bearing clouds blow in from the Arabian Sea towards the Western Ghats.
The Himalayan slopes having Scanty rainfall.
Kutch and West Rajasthan having rainfall below 50 cm.
Southern Haryana, south-east Punjab and Ladakh also having below 50cm.

In studying the natural vegetation of India, variation in species and luxuriance of vegetation from place to place, thus, depend to a large extent on the distribution of rainfall.
The per capita forest cover of India is 0.06 hectare while the global per capita forest cover is 0.6 hectare.
As per India State of Forest Report 2011, the Forest and Tree cover of the country is 78.29 million ha, which is 23.81% of the geographical area of the country.
In comparison to the 2009 assessment, after taking into account the interpretational changes, there is a decrease of 367 square km in country's forest cover.

15 states have registered aggregate increase of 5000sqkm in their forest cover with Punjab leading with increase of 100sqkm.
12 states/UTs (mainly the NE states) have shown decrease to the extent of 867sdkm.
The state of Madhya Pradesh has the largest forest cover in the country at 77.700 square km followed by Arunachal Pradesh at 67, 410 square km.
In terms of percentage of forest cover in relation to total geographical area, Mizoram tops with 90. 68% followed by Lakshadweep with 84. 56%.
The total growing stock of India's forests and trees outside forests is estimated as 6047.15 million cu m i.e. 4498.73 million cu m inside the recorded forest area and 1548.42 million cu m outside the recorded forests.

Forests help to check soil erosion on hill slopes in upper catchment areas of rivers which contribute to the control of floods increase rainfall and improve local climate produce timber, fuel and industrial raw materials.
India provides about 8% of the world's hardwood and ranks third alter Brazil and Indonesia.
State having its maximum geographical area under dense forest cover Arunachal Pradesh.
State having lowest area under forest cover Haryana.
Slate having largest area of forest cover In India Madhya Pradesh.

They are dense luxuriant in growth, look evergreen, but shed leaves at different pans of the year.
They are prevalent in areas when the rainfall Is over 200 cm, 77% or more humidity and 25° to 27°C of annual temperature, found in the north-east, eastern regions of sub-tropical Himalayas (Tarai), western portion of western ghats, Andaman and Nicobar islands.
They provide hardwood like teak, rosewood, ebony and bamboo etc.
These are coniferous forests having needle-shaped leaves.

Found in the areas where annual rainfall is 250 cm or above.
These forests occur in North-eastern states.
Andaman and Nicobar islands and western part of western ghats.

Found in the areas where the annual rainfall is below 200 cm.
They are evergreen with mixed deciduous. The temperature ranges from 24°C to 27°C with 80% humidity.
Heavy barks, climbers and buttersed trunks are found.
They occur in Upper Assam lower eastern Himalayas Orissa and Andaman and Nicobars islands.

They occur where the annual rainfall is 150 to 200 cm with mean annual temperature about 26° to 27°C and humidity varies with 60 to 80 percent found In the interior of the Indian Plateau and the Siwalik, east of river Yamuna.
Sal Teak, Tendu, Sissoo, Mahua, Sandal and Shisam are important trees.
Trees shed their leaves during spring and early summer.

They known as tidal forests or mangrove forests.
They occur around the tidal creeks and along the delta of river Ganga, Mahanadi, Krishna and Godavari.
These trees are mainly evergreen have profuse growth and stilt like roots.
The densest trees are found in the great Sunderban delta where the Sundari tree in abundance is found.
Rhizophora and Nipa fruitous (a type of palm) also grow in these forests.

These forests found from foothills of Himalayas to Kanyakumari and comprise important trees like Teak Tendu, Amaltas, Khari, Palas, Rosewood and Axlewood.
The tracks of these forests has a low canopy of grasses and shrubs in some places which has been cleared for agriculture and casuarina plantations.

Riparian Forests common in wet places particularly along the river banks and other wet lands where rainfall is less than 50 cm.
Neem, Shisham, Babool, Pipal are common in such places.
Alpine Forests cover the alpine areas in Himalayas i.e., at the height of 2880 m to 3700 m.
Dwarf shrubs of Juniper, Fir, Pine, Birch and Rhododendron are the main trees on southern Himalayan slopes.

They are found in

1. Low land or grass land
2. Upland or hilly' grass land
3. Riverine grass land

Low land grass land occur in the regions where the rainfall is 30 to 200 cm, with high temperature in summer, found in Punjab, Uttar Pradesh, Haryana, Bihar and North-west Assam.
Upland Grasses are found at a height of 1000 m in Himalayas and in the clear forest areas of western ghats (Karnataka).
Riverine grasses are found in northern part of India.