A day after Rajasthan's Phalodi recorded the country's highest temperature ever of 51°C, the India Meteorological Department said the frequency of severe heat waves had increased sharply in the past 15 years. Most heat-affected states have no plan in place to prevent mortality and morbidity associated with extreme heat. IMD officials said the average frequency of severe heat waves had doubled from 50 days a year across India until 2000, to about 100 in the 2001-2010 decade. The figures are cumulative numbers from all IMD stations. So, if there are 10 severe heat wave days in two cities simultaneously, it's counted as 20.

The Indian Institute of Public Health (IIPH), which has developed a heat action plan for Ahmedabad and helped cities in Maharashtra develop theirs, has advised the Union health ministry to ensure that similar plans are implemented in all states affected by heat waves.

As of now Maharashtra, Gujarat, Telangana and Andhra Pradesh have started a heat action plan.

"Mortality increases as soon as there is a heat wave. For instance, on Thursday when it recorded 48 degrees in Ahmedabad, there were 130 deaths compared to 100 deaths daily on an average. During the 2010 heat wave, there were 310 deaths in a day and about 800 deaths in total in the following week," said Dr Dileep Mavalankar, director, IIPH, Gandhinagar.

"Since the frequency of heat waves is increasing due to climate change, we have been pursuing the implementation of heat plans with the government. Ideally local government administration or municipalities should be in charge of it," Mavalankar said.