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Climate of India

Climate of India

Generally, India's climate is defined by three seasons - the hot, the wet (monsoon) and the cool, each of which can vary in duration from north to south. The most pleasant time to visit most places is during the cooler period November to around mid-February.

India has tropical weather. One cannot speak of the climate of India, or else one must speak of several different India's. The subcontinent has eight climatic zones all of which only have the monsoon rains in common. But even the monsoon comes to different parts of the country at different times. And you can fly in the space of a couple of hours through a range of weather from the cold crisp air of the mountains to the burning dry heat of the Rajasthan Desert where summer temperature regularly reach 45°C and beyond.

It is beautiful to see the sand dunes shift and move to the will of the winds, but not at all pleasant to be caught in a sand strom coming off the Thar. In winter Rajasthan is dry and cold and the skies a translucent blue. There is little rain and the monsoon winds often pass Rajasthan by leaving the prickly thorny bushes, acacia trees and other native vegetation to pick up what little dew the night bring with it. Pumps and tube wells lift water for agricultural irrigation but farmers often get only a few distribution of water, particularly in the more arid areas of Jodhpur, Bikaner and Jaisalmer, is systematically organized.

The wheat and sugarcane growing areas of the Punjab, Haryana and parts of western Uttar Pradesh suffer from drastic extremes in climate. It can be very cold from December - January, very dry and hot from the end of March till June, very hot and humid till the monsoons arrive from July through September. The rest of the year is comfortably pleasant. The fields are full of mustard flowers, the air is redolent of sugarcane being crushed and molasses on the boil.

Across the Gangetic plain, the summer months are an interminable heat haze. From Gwalior through Bhopal and Raipur to Patna and Nagpur, temperature begin to rise in March and by May they hover around 45°C. In the fields, the earth actually shows deep cracks. In Bihar, for example, a terrible drought with near famine conditions occurred a few year ago. The fickle winds had taken the clouds several thousands miles westward to the Punjab, and India's granary produced bumper crops that same year!

India is home to an extraordinary variety of climatic regions, ranging from tropical in the south to temperate and alpine in the Himalayan north, where elevated regions receive sustained winter snowfall. The nation's climate is strongly influenced by the Himalayas and the Thar Desert. The Himalayas, along with the Hindu Kush mountains in Pakistan, prevent cold Central Asian katabatic winds from blowing in, keeping the bulk of the Indian subcontinent warmer than most locations at similar latitudes. Simultaneously, the Thar Desert plays a role in attracting moisture-laden southwest summer monsoon winds that, between June and October, provide the majority of India's rainfall. Four major climatic groupings predominate, into which fall seven climatic zones that, as designated by experts, are defined on the basis of such traits as temperature and precipitation. Groupings are assigned codes (see chart) according to the Köppen climate classification system.

Tropical wet
A tropical rainy climate covers regions experiencing persistent warm or high temperatures, which normally do not fall below 18 °C (64 °F). India hosts two climatic subtypes that fall under this group. The most humid is the tropical wet monsoon climate that covers a strip of southwestern lowlands abutting the Malabar Coast, the Western Ghats, and southern Assam. India's two island territories, Lakshadweep and the Andaman and Nicobar Islands, are also subject to this climate. Characterised by moderate to high year-round temperatures, even in the foothills, its rainfall is seasonal but heavy—typically above 2,000 millimetres (79 in) per year. Most rainfall occurs between May and November; this is adequate for the maintenance of lush forests and other vegetation throughout the remainder of the year. December to March are the driest months, when days with precipitation are rare. The heavy monsoon rains are responsible for the extremely biodiverse tropical wet forests of these regions.

In India, a tropical wet and dry climate is more common. Significantly drier than tropical wet zones, it prevails over most of inland peninsular India except for a semi-arid rain shadow east of the Western Ghats. Winter and early summer are long, dry periods with temperatures averaging above 18 °C (64 °F). Summer is exceptionally hot; temperatures in low-lying areas may exceed 50 °C (122 °F) during May, leading to heat waves that can each kill hundreds of Indians. The rainy season lasts from June to September; annual rainfall averages between 750–1500 millimetres (30–59 in) across the region. Once the dry northeast monsoon begins in September, most precipitation in India falls on Tamil Nadu, leaving other states comparatively dry.
Tropical dry

A tropical arid and semi-arid climate dominates regions where the rate of moisture loss through evapotranspiration exceeds that from precipitation; it is subdivided into three climatic subtypes. The first, a tropical semi-arid steppe climate, predominates over a long stretch of land south of Tropic of Cancer and east of the Western Ghats and the Cardamom Hills. The region, which includes Karnataka, inland Tamil Nadu, western Andhra Pradesh, and central Maharashtra, gets between 400–750 millimetres (16–30 in) annually.

It is drought-prone, as it tends to have less reliable rainfall due to sporadic lateness or failure of the southwest monsoon. North of the Krishna River, the summer monsoon is responsible for most rainfall; to the south, significant post-monsoon rainfall also occurs in October and November. In December, the coldest month, temperatures still average around 20–24 °C (68–75 °F). The months between March to May are hot and dry; mean monthly temperatures hover around 32 °C, with 320 millimetres (13 in) precipitation. Hence, without artificial irrigation, this region is not suitable for permanent agriculture.

The Rann of Kutch, a vast salt marsh south of the Thar Desert in Gujarat. During the monsoon season, the region fills with standing waters.
The Rann of Kutch, a vast salt marsh south of the Thar Desert in Gujarat. During the monsoon season, the region fills with standing waters.

East of the Thar Desert, the region running from Punjab and Haryana to Kathiawar experiences a tropical and sub-tropical steppe climate. The zone, a transitional climatic region separating tropical desert from humid sub-tropical savanna and forests, experiences temperatures that are less extreme than those of the desert. Average annual rainfall is 30–65 centimetres (12-26 in), but is very unreliable; as in much of the rest of India, the southwest monsoon accounts for most precipitation. Daily summer temperature maxima rise to around 40 °C (104 °F). The resulting natural vegetation typically comprises short, coarse grasses.

Subtropical humid
Most of Northeast India and much of North India are subject to a humid sub-tropical climate. Though they experience hot summers, temperatures during the coldest months may fall as low as 0 °C (32 °F). Due to ample monsoon rains, India has only one subtype of this climate, Cfa (under the Köppen system). In most of this region, there is very little precipitation during the winter, owing to powerful anticyclonic and katabatic (downward-flowing) winds from Central Asia. Due to the region's proximity to the Himalayas, it experiences elevated prevailing wind speeds, again from the influence of Central Asian katabatic movements.

Humid subtropical regions are subject to pronounced dry winters. Winter rainfall—and occasionally snowfall—is associated with large storm systems such as "Nor'westers" and "Western disturbances"; the latter are steered by westerlies towards the Himalayas. Most summer rainfall occurs during powerful thunderstorms associated with the southwest summer monsoon; occasional tropical cyclones also contribute. Annual rainfall ranges from less than 1,000 millimetres (39 in) in the west to over 2,500 millimetres (98 in) in parts of the northeast. As most of this region is far from the ocean, the wide temperature swings more characteristic of a continental climate predominate; the swings are wider than in those in tropical wet regions, ranging from 24 °C (75 °F) in north-central India to 27 °C (81 °F) in the east.

Montane
India's northernmost fringes are subject to a montane, or alpine, climate. In the Himalayas, the rate at which an air mass's temperature falls per kilometre (3,281 ft) of altitude gained (the adiabatic lapse rate) is 5.1 °C/km.[20] In terms of environmental lapse rate, ambient temperatures fall by 0.6 °C (1.1 °F) for every 100 metres (328 ft) rise in altitude. Thus, climates ranging from nearly tropical in the foothills to tundra above the snow line can coexist within several dozen miles of each other. Sharp temperature contrasts between sunny and shady slopes, high diurnal temperature variability, temperature inversions, and altitude-dependent variability in rainfall are also common. The northern side of the western Himalayas, also known as the trans-Himalayan belt, is a region of barren, arid, frigid, and wind-blown wastelands. Most precipitation occurs as snowfall during the late winter and spring months.

Areas south of the Himalayas are largely protected from cold winter winds coming in from the Asian interior. The leeward side (northern face) of the mountains receives less rain while the southern slopes, well-exposed to the monsoon, get heavy rainfall. Areas situated at elevations of 1,070–2,290 metres (3,510–7,510 ft) receive the heaviest rainfall, which decreases rapidly at elevations above 2,290 metres (7,513 ft). The Himalayas experience their heaviest snowfall between December and February and at elevations above 1,500 metres (4,921 ft). Snowfall increases with elevation by up to several dozen millimetres per 100 metre (~2 in; 330 ft) increase. Elevations above 5,000 metres (16,404 ft) never experience rain; all precipitation falls as snow.
Seasons

Season In India

Winter, occurring between January and March. The year's coldest months are December and January, when temperatures average around 10–15 °C (50–59 °F) in the northwest; temperatures rise as one proceeds towards the equator, peaking around 20–25 °C (68–77 °F) in mainland India's southeast.

Summer or pre-monsoon season, lasting from March to June (April to July in northwestern India). In western and southern regions, the hottest month is April; for northern regions, May is the hottest month. Temperatures average around 32–40 °C (90–104 °F) in most of the interior.

Monsoon or rainy season, lasting from June to September. The season is dominated by the humid southwest summer monsoon, which slowly sweeps across the country beginning in late May or early June. Monsoon rains begin to recede from North India at the beginning of October.

Post-monsoon season, lasting from October to December. South India typically receives more precipitation. Monsoon rains begin to recede from North India at the beginning of October. In northwestern India, October and November are usually cloudless. Parts of the country experience the dry northeast monsoon.

The Himalayan states, being more temperate, experience an additional two seasons: autumn and spring. Traditionally, Indians note six seasons, each about two months long. These are the spring , summer , monsoon season , early autumn, late autumn , and winter. These are based on the astronomical division of the twelve months into six parts. The ancient Hindu calendar also reflects these seasons in its arrangement of months.