Climates and disasters

India's weather can bring cyclones, floods, landslides and other disasters that hurt lives, farms, roads and buildings, and local economies.

Cyclones strike the coast every year, especially the east coast. The IMD tracks them: how they form, grow and where they'll land. How one forms: pressure over the sea drops lower than all around. Air rushes in from every side, bringing moisture. If the low is very strong and winds very fast, the winds spin inwards around the centre, forming clouds: a cyclone. The calm, cloudless centre is the eye of the cyclone. (Clouds are masses of tiny water drops, ice crystals or both, floating in the air.)

The National Disaster Response Force (NDRF) is specially trained to rescue people in natural and human-made disasters. It has battalions in 12 places across India.

Floods: water spills onto normally dry land, from very heavy rain the ground can't soak up, or rivers and lakes overflowing. Uttar Pradesh, Bihar, Kerala, Andhra Pradesh and Assam are especially at risk. In the Himalayas, a glacial lake held back by rock and ice can burst if glaciers melt too fast or rain is too heavy: a glacial burst. In 2013, one hit Uttarakhand after days of rain; landslides followed, the area around Kedarnath temple was destroyed, and about 6,000 people, many of them pilgrims, died.

Cities flood too: drains are overloaded, buildings block natural waterways, and concrete and tar don't let water soak in.

Landslides (rock, soil and debris collapsing suddenly) happen after heavy rain or earthquakes, in Himachal, Uttarakhand, Sikkim, Arunachal Pradesh and the Western Ghats. Cutting down forests and careless building make them more likely. Forest fires spread fast in dry, windy weather; human carelessness often starts them. Each disaster is part natural, part human, so each can be partly prevented.