What are heat waves and cold waves?

Heat waves : During the months of March to July, spoil of abnormally hot weather is occasionally experienced in certain parts of India. These spells move from one region to another and are called heat waves. They have their maximum temperatures more than 6°C above normal. A heat wave with a maximum temperature of 8°C or more above the normal is considered to be severe. Heat waves occur in most of the country except the southern states of Kerala and Tamil Nadu, Pondicherry and Lakshadweep, Andaman and Nicobar Islands.

Cold waves : During the months of November and April, cold and dry winds blow in northwest India. Whon they attain minimum temperature below 6°C from the normal they are called cold waves. Severe cold waves occur in Jammu & Kashmir, Punjab, Uttar Pradesh, Rajasthan and Madhya Pradesh. The frequency of severe cold waves decreases towards the east and south. The southern states are almost free from cold waves.