The Hot Weather Season

The hot weather season is the first of the three main seasons of the Indian year, and it is a season of intense, rising heat across most of the country. Its character is set by the northward march of the sun, the shifting of the wind belts, and the arrival of localised storms that bring the only relief before the monsoon breaks.

The Setting

By March, the sun begins its apparent northward movement, crossing the equator and heading towards the Tropic of Cancer. The highest temperatures are no longer near the equator but shift northwards, settling over the north-western parts of the country. This is the season of steadily rising temperatures, falling air pressure, and drying winds.

Temperature Patterns

The heat builds up progressively through March, April and May. The interior of the peninsula records the highest temperatures, with the north-western region — parts of Rajasthan, Gujarat and Madhya Pradesh — experiencing the most intense heat. In May, daytime temperatures in these areas can cross 45 degrees Celsius. The Deccan plateau and the central highlands also get very hot, while the coastal regions remain somewhat cooler because of the moderating influence of the sea. The southern tip of the peninsula, being closer to the equator, does not heat up as much as the interior.

Pressure and Winds

As the land heats up, a low-pressure area develops over the north-western part of the country. This thermal low intensifies through the season. Winds begin to blow towards this low-pressure centre from all directions, but they are dry and hot. Over the northern plains, a hot, dry and dusty wind called the loo blows during the day. It is especially strong in the afternoons and can be dangerous, sometimes causing heat strokes.

The Arrival of Thunderstorms

The heat, however, is not without its dramatic interruptions. Towards the end of the hot weather season, localised thunderstorms begin to develop. These are caused by the intense heating of the ground, which leads to strong convection currents. The rising hot air cools rapidly, forming cumulonimbus clouds that bring sudden, violent thunderstorms.

These storms are known by different local names:

• In West Bengal and the north-eastern states, they are called Kal Baisakhi — the storms of the month of Baisakh (mid-April to mid-May). They bring welcome rain and often strong winds and hail.
• In Assam, these pre-monsoon showers are known as Tea showers, because they are beneficial for the tea crop.
• In Karnataka, the local thunderstorms are called Mango showers, as they help the mango crop ripen early.

These localised storms provide some relief from the oppressive heat, but they are short-lived and do not change the overall character of the season.

Dust Storms and the End of the Season …