Climate of India

India has many kinds of weather because it is a big country with different landscapes. From dry deserts in the west to cold mountains in the north, the weather changes a lot from place to place. The north part, called the Indo-Gangetic Plains, has warm and wet weather, while the south and east are usually hot and rainy, with thick forests in some areas.

The Himalayas in the north and the Thar Desert in the west affect India's weather. The Himalayas block cold winds from the north, keeping most of North India warm in winter and hot in summer. South India is usually warmer and more humid because it has coastlines, but some mountain towns like Ooty can get cold.

India has four main seasons: winter, summer, monsoon, and post-monsoon. Because of its location near the Tropic of Cancer, India is mostly tropical, but weather can be unpredictable. Sometimes there are long dry periods, very hot summers, heavy rains, or strong storms.

Paleoclimate

History

During the Triassic period, between 251 and 199.6 million years ago, the land that is now India was part of a huge landmass called Pangaea. Even though it was far south, India had a warm and humid climate with clear seasons. Later, India joined another large landmass named Gondwana. This position gave India a mild climate that helped many plants and animals thrive.

The world, including India, was warmer during the Mesozoic era. Later, cooling led to large ice sheets that moved toward India. The movement of the Indian Plate created the Deccan Traps, a huge lava flow about 60–68 million years ago. This event may have played a role in a major global change that affected India's climate.

The rise of the Himalayas blocked cold air from Central Asia, making India's climate warmer and more tropical.

In more recent times, during the Holocene epoch (about 4,800 to 6,300 years ago), parts of what is now the Thar Desert had enough water to support lakes all year. This was likely because of heavier winter rains and stronger monsoons. The climate in Kashmir also became cooler around 2.6 to 3.7 million years ago.

Regions

India has many different climates. In the south, it is tropical, while in the northern Himalayan region, the climate becomes temperate and even alpine, with higher areas getting snow in winter. The Himalayas and the Thar Desert greatly influence the nation's climate. The Himalayas prevent cold winds from Central Asia, keeping most of the country warmer than places at similar latitudes. The Thar Desert helps bring in moist southwest monsoon winds from June to October, which bring most of India's rain.

India has four main climate groups. These groups include seven climatic zones, defined by traits like temperature and rainfall. These groups are based on the Köppen climate classification system.

Tropical

A tropical rainy climate covers areas where temperatures stay warm or hot, usually never dropping below 18 degrees Celsius (64 °F). India mainly has two types: tropical monsoon climate and tropical savanna climate.

The tropical wet climate, also called the tropical monsoon climate, covers southwestern lowlands near the Malabar Coast, the Western Ghats, and southern Assam. India's island territories, Lakshadweep and the Andaman and Nicobar Islands, also have this climate. Temperatures stay moderate to high year-round, even in the foothills. Rainfall is seasonal but heavy—usually over 2,000 millimetres (79 inches) each year. Most rain falls between May and November, supporting lush forests and other vegetation through the drier months. December to March are the driest months, with few rainy days. The heavy monsoon rains help create the rich biodiversity of tropical wet forests in these areas.

A tropical savanna climate is more common in India. It is drier than the tropical monsoon climate and covers most of inland peninsular India, except for a semi-arid area east of the Western Ghats. Winters and early summers are long and dry, with temperatures above 18 °C (64 °F). Summers are very hot; temperatures in low areas can reach over 50 °C (122 °F) in May, sometimes causing heat waves. The rainy season runs from June to September, with annual rainfall between 750 and 1,500 mm (30 and 59 in). After September, most rain in India falls on Tamil Nadu and Puducherry, leaving other states drier.

The Ganges Delta is mostly in the tropical wet climate zone. It gets between 1,500 and 2,000 mm (59 and 79 in) of rain each year in the west, and 2,000 to 3,000 mm (79 to 118 in) in the east. January is usually the coolest month, with average temperatures from 14 to 25 °C (57 to 77 °F). April and May are the warmest, with averages from 25 to 35 °C (77 to 95 °F). July is typically the coldest and wettest month, with over 330 mm (13 in) of rain.

The Nicobar Islands also have a Tropical rainforest climate.

Arid and semi-arid regions

Arid and semi-arid climates dominate areas where moisture loss is greater than rainfall.

A semi-arid steppe climate is found over a long stretch of land south of the Tropic of Cancer and east of the Western Ghats and the Cardamom Hills. This region includes Karnataka, inland Tamil Nadu, western Andhra Pradesh, and central Maharashtra. It receives between 400 and 750 millimetres (15.7 and 29.5 in) of rain each year. The region is prone to droughts because rainfall is unreliable, often delayed or missed altogether during the southwest monsoon. Karnataka has three zones: coastal, north interior, and south interior. The coastal zone gets the most rain, about 3,638 mm (143.2 in) a year, much more than the state average of 1,139 mm (44.8 in). Agumbe in Shivamogga district gets the second-highest annual rainfall in India. North of the Krishna River, the summer monsoon brings most of the rain; south of it, there is also significant rain in October and November. In December, the coldest month, temperatures average around 20–24 °C (68–75 °F). March to May are hot and dry, with temperatures around 32 °C (90 °F) and about 320 mm (12.6 in) of rain. Without irrigation, this area is not good for farming.

Most of western Rajasthan has an arid climate. Cloudbursts bring almost all of the region's rain, totaling less than 300 mm (11.8 in) a year. These bursts happen when monsoon winds reach the area in July, August, and September. Rainfall is very unpredictable; some places get rain one year and none for several years. Summers in May and June are extremely hot, with temperatures around 35 °C (95 °F) and sometimes over 50 °C (122 °F). Winters can be cold, with temperatures dropping below freezing due to cold air from Central Asia. There is a big difference between day and night temperatures in summer, and this difference grows in winter. There is a small desert near Adoni in Andhra Pradesh, the only desert in South India, with summer temperatures up to 47 °C (117 °F) and winter temperatures around 18 °C (64 °F).

In Gujarat, the climate varies. Winters are mild and dry, with daytime temperatures around 29 °C (84 °F) and nights around 12 °C (54 °F). Summers are hot and dry, with days around 41 °C (106 °F) and nights no lower than 29 °C (84 °F). Before the monsoon, temperatures are similar but high humidity makes it feel uncomfortable. The monsoon brings relief, with temperatures around 35 °C (95 °F) and very high humidity; nights are around 27 °C (81 °F). Most rain falls during this time, and it can cause severe floods. The sun is often hidden during the monsoon.

East of the Thar Desert, the Southwest Punjab–West Haryana–Kathiawar region has a tropical and sub-tropical steppe climate. Haryana's climate is similar to other northern plain states, with very hot summers up to 45 °C (113 °F) and cold winters as low as 0 °C (32 °F). May and June are the hottest months; December and January are the coldest. Rainfall varies, with the Shivalik Hills being the wettest and the Bagar region the driest. About 80% of the rain comes in the monsoon season from July to September, which can cause flooding. Punjab has extreme temperatures, ranging from −2 to 40 °C (28 to 104 °F), but can reach 47 °C (117 °F) in summer and drop to −4 °C (25 °F) in winter. This area separates the tropical desert from humid subtropical savanna and forests, with less extreme temperatures than the desert. Annual rainfall is 300–650 mm (11.8–25.6 in), mostly during the southwest monsoon. Summer highs are around 40 °C (104 °F). The natural vegetation here is usually short, tough grasses.

Humid subtropical

Most of Northeast India and much of North India have a humid subtropical climate and a subtropical highland climate. They have warm to hot summers, but winter temperatures can drop to 0 °C (32 °F). These areas get plenty of monsoon rain, with two subtypes under the Köppen system. In most of this region, winters have very little rain due to strong winds from Central Asia.

Humid subtropical regions have dry winters. Spring rain comes from large storms called "Western disturbances," which move from the west towards the Himalayas and Punjab-Haryana Plains. These storms can bring hail and damage crops. Most summer rain falls during strong monsoon thunderstorms from July to September, caused by the tropical rain belt. Occasionally, tropical cyclones also add to the rainfall. Annual rain ranges from less than 1,000 mm (39 in) in the west to over 2,500 mm (98 in) in parts of the northeast. Because much of this region is far from the ocean, temperatures change more widely than in tropical areas, from 24 °C (43 °F) in the north to 27 °C (49 °F) in the east. The main plants in this area are subtropical broadleaf forests, which are evergreen in the Brahmaputra Valley and Lower Gangetic Plains where rainfall is higher, and deciduous in the Upper Gangetic Plains and Punjab-Haryana Plains where rainfall is less. This climate zone includes major cities such as New Delhi, Lucknow, Ambala, Chandigarh, Patiala, Siliguri, and Guwahati.

Montane

India's northern areas have a montane, or alpine, climate. In the Himalayas, temperature decreases by about 9.8 °C for every kilometre of height gained. Environmental temperatures drop by 6.5 °C for every 1,000 metres of altitude. This means climates can change from nearly tropical in the foothills to tundra above the snow line, all within a few hundred metres. There are big temperature differences between sunny and shady slopes, large daily temperature changes, temperature inversions, and changes in rainfall with altitude.

The northern side of the western Himalayas, known as the trans-Himalayan belt, has a cold desert climate. It is a barren, dry, very cold, and windy area. Areas south of the Himalayas are protected from cold winter winds from Asia. The northern side gets less rain.

The southern slopes of the western Himalayas, facing the monsoon, get heavy rain. Areas between 1,070 and 2,290 metres (3,510 to 7,510 ft) get the most rain, which decreases above 2,290 metres (7,513 ft). Most rain falls as snow in late winter and spring. The Himalayas get their heaviest snow between December and February at heights above 1,500 metres (4,921 ft). Snowfall increases with altitude, sometimes by several dozen millimetres for every 100 metres (330 ft) up. Above 6,000 metres (19,685 ft), it never rains; all precipitation is snow.

Seasons

The India Meteorological Department (IMD) says India has four main seasons:

• Winter, from December to February. December and January are the coldest months, with temperatures around 10–15 °C (50–59 °F) in the northwest. Temperatures rise toward the equator, reaching about 20–25 °C (68–77 °F) in southern India.
• Summer or pre-monsoon, from March to June. April is the hottest month in western and southern regions, while May is hottest in northern regions. Temperatures can reach around 32–40 °C (90–104 °F) in many areas.
• Monsoon or south-west monsoon, from June to September. This season brings humid winds and heavy rains across the country, starting in late May or early June. North India’s rains usually end in October, while South India gets more rainfall.
• Post-monsoon or north-east monsoon, from October to November. In northern India, these months are often clear and cloudless. Tamil Nadu gets most of its yearly rain during this time.

The Himalayan and Upper Gangetic Plains have an extra season called spring, which happens at the start of summer in southern India. Traditionally, some North Indians recognize six seasons, each lasting about two months. The ancient Hindu calendar reflects these seasons in its monthly arrangement.

Winter

Once the monsoons end, temperatures drop across India. December and January are the coldest months, especially in the Indian Himalayas. Northwestern India stays clear and cool, but "western disturbances" bring rain and snow from the Mediterranean Sea.

Himachal Pradesh has varied climates due to its altitude. Snow falls at heights of nearly 3,000 meters from December to March, and above 4,500 meters, snow remains year-round. Spring starts in mid-February, bringing pleasant weather. The rainy season begins in June.

Most of North India, including the Indo-Gangetic Plain and Madhya Pradesh, rarely sees snow. Winter temperatures in Delhi range from 16 to 21 °C (61 to 70 °F) during the day and 2–8 °C (36–46 °F) at night. In Punjab, nights can drop below freezing, especially in Amritsar. Fog is common.

In Bihar, hot weather starts in the middle of June. The rainy season begins in June, with July and August being the rainiest months. Eastern India is milder but gets colder as you move northwest. Patna has highs from 18 °C to 23 °C (64 °F to 73 °F) and lows from 7 °C to 10 °C (45 °F to 50 °F), while Kolkata has highs from 22 °C to 27 °C (72 °F to 80 °F) and lows from 12 °C to 15 °C (54 °F to 59 °F). Bhopal in Madhya Pradesh has lows of 9 °C (48 °F) and highs of 24 °C (75 °F).

The Himalayas greatly affect India’s climate by blocking cold Arctic winds. They also influence monsoon winds. The Himalayas have large glaciers and are the source of ten major Asian rivers. Sikkim, Arunachal Pradesh, and parts of West Bengal, especially Darjeeling, sometimes see snowfall.

In South India, areas like Maharashtra, Karnataka, and Andhra Pradesh have cooler weather. Coastal areas are warmer, with highs around 30 °C (86 °F) and lows around 21 °C (70 °F).

Summer

Summer starts in mid-April in northwestern India and lasts until late June, but in most of the country, it runs from March to May, sometimes lasting until mid-June. The sun’s rays heat up the north, with May and June being the hottest months. Temperatures can reach 50 °C (122 °F) or more in some places.

Strong, hot, dry winds called the Loo blow during the day. In North India, pre-monsoon storms called "Nor'westers" bring large hailstones. By May, most of India’s interior has temperatures over 32 °C (90 °F), with maximums often above 40 °C (104 °F).

Higher altitudes, like the Deccan Plateau, are cooler. Hill stations such as Ootacamund ("Ooty") and Kalimpong offer relief with average maximum temperatures around 25 °C (77 °F). The loo wind blows from the west in northern and western India. Tornadoes are rare but can occur in a corridor from northeastern India to Pakistan.

Monsoon

The southwest summer monsoon is India’s main rainy season, lasting four months and providing over 80% of the country’s rainfall. It begins with winds from the southern Indian Ocean.

The monsoon arrives in two branches: the Bay of Bengal branch and the Arabian Sea branch. It typically reaches the Andaman and Nicobar Islands by 25 May, the mainland near Malabar Coast by 1 June, Mumbai by 9 June, and Delhi by 29 June. The Bay of Bengal branch moves toward the Indo-Gangetic Plain, while the Arabian Sea branch heads toward the Himalayas. By early July, the whole country experiences monsoon rains, with South India getting more rain on average than North India, but Northeast India receives the most.

Monsoon rains are vital for the Indian economy because Indian agriculture employs many people. Good monsoons help the economy grow, while weak monsoons can harm agriculture.

Post-monsoon

In the post-monsoon or autumn months of October to December, a different monsoon brings dry, cool air to much of India. Winds cross the Himalayas and move southwest, leading to clear skies. This period marks the change from wet to dry conditions.

The northeast monsoon runs from September to October through the post-monsoon season, ending between December and January. These winds lose their moisture over the ocean and cross India from northeast to southwest. The Bay of Bengal’s shape adds moisture before the winds reach Cape Comorin and Tamil Nadu, giving the state and parts of Kerala significant rain during this time. Some parts of West Bengal, Orissa, Andhra Pradesh, Karnataka, and Mumbai also get minor rain from the northeast monsoon.

Statistics

Here are temperature and rainfall details for some cities in India. They show the different kinds of weather found across the country. The data is grouped by the seasons used by India's weather department, and also includes yearly averages.

Extremes

India has many different temperatures. The coldest temperature ever was −45.0 °C (−49 °F) in Dras, Ladakh. Even colder places exist on Siachen Glacier near Bilafond La and Sia La.

The hottest temperature ever was 51.0 °C (124 °F) in Phalodi, Rajasthan, on May 16, 2016.

Some places in India get a lot of rain. The village of Mawsynram in Meghalaya gets the most rain in Asia, maybe in the world, with an average of 11,861 millimetres (467 in) each year. On July 26, 2005, Mumbai got 944 mm (37 in) of rain in one day, causing big floods.

Some parts of India also get a lot of snow. In February 1967, Gulmarg in Jammu and Kashmir got 8.4 metres (27.6 ft) of snow in one month.

Climate change

India has many kinds of weather because it is a large country with many different landscapes. In the west, it can be dry. In the north near the Himalayas, the weather changes a lot depending on how high up you are. It can be very cold or even icy.

Atmospheric pollution

Main article: Air pollution in India

Thick haze and smoke from burning plants in northwestern India and pollution from big cities in northern India often gather over the Ganges Basin. Winds carry tiny particles towards eastern India and the Bay of Bengal. Dust and black carbon, blown by winds along the edges of the Himalayas, can trap heat and warm the air above the Tibetan Plateau. This warming makes the air rise and adds more moisture high in the sky.