"There were only nine a few years back but currently 23 are recognised as heatwave-prone states," he said. "Cities have become heat islands, so a lot of them are drafting their own plans."
He said the plans include reducing people's exposure to heat, arranging drinking water in public places and other interventions.
The western state of Maharashtra, home to India's financial capital Mumbai, has also planned to modify market hours, provide public shelters, sprinkle mist in public places and keep ice bags at public health centres, according to the NDMA website.
Long-term measures include planting more trees, rainwater harvesting, providing shelter for traffic police and using green nets for shade in market areas, it adds.