Factors Determining the Climate of India

India’s climate is not a single, uniform system. It is the product of several geographical controls working together — the country’s position on the globe, its physical features, and its relationship with the surrounding seas. Each factor shapes temperature, pressure, wind direction, and rainfall in its own way, and together they explain why the coast and the interior, the mountains and the plains, experience such different weather.

Latitude

The Tropic of Cancer passes through the central part of India in an east-west direction. This single line divides the country into two distinct climatic zones. The part lying south of the Tropic of Cancer falls in the tropical zone. Being nearer to the equator, this region experiences high temperatures throughout the year, with only a small daily and annual range of temperature. The northern part of India, lying north of the Tropic of Cancer, falls in the sub-tropical and temperate zone. Being farther from the equator, this region experiences an extreme climate, with a high daily and annual range of temperature. In simple terms, the south is warm and relatively steady, while the north swings between hot summers and cold winters.

The Himalayan Mountains

The lofty Himalayas in the north, along with their extensions, act as an effective climatic divide. This towering mountain chain provides an invincible shield that protects the Indian subcontinent from the cold northern winds. These cold and chilly winds originate near the Arctic circle and blow across central and eastern Asia. Without the Himalayas, these winds would sweep into the subcontinent and make winters far more severe. The Himalayas also play a second, equally vital role: they trap the monsoon winds, forcing them to shed their moisture within the subcontinent. The mountains thus both block the cold and hold the rain.

Distribution of Land and Water

India is flanked by the Indian Ocean on three sides in the south and girdled by a high and continuous mountain-wall in the north. Water heats up and cools down slowly compared to land. This differential heating of land and sea creates different air pressure zones in different seasons in and around the Indian subcontinent. In summer, the land heats quickly and develops low pressure, while the sea remains relatively cooler; in winter, the reverse happens. This difference in air pressure causes a reversal in the direction of monsoon winds — the defining feature of India’s climate.

Distance from the Sea

With a long coastline, large coastal areas have an equable climate — moderate temperatures, neither too hot nor too cold. Areas in the interior of India are far away from the moderating influence of the sea, and such areas have extremes of climate. The book makes this contrast vivid: the people of Mumbai and the Konkan coast have hardly any idea of extremes of temperature or the seasonal rhythm of weather. On the other hand, the seasonal contrasts in weather at places in the interior of the country, such as Delhi, Kanpur and Amritsar, affect the entire sphere of life — clothing, housing, food habits, and daily routines all change with the seasons.

Altitude

Temperature decreases with height. Due to thin air, places in the mountains are cooler than places on the plains. The book gives a striking example: Agra and Darjiling are located on the same latitude, but the January temperature in Agra is 16 °C, whereas it is only 4 °C in Darjiling. The difference of 12 °C is entirely due to altitude, not latitude.

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