The temperature in New Delhi reached 43.5ºC on Thursday, the capital's hottest April day in 12 years, and was forecast to reach 44ºC on Friday and rise even higher at the weekend, according to the India Meteorological Department.
Parts of India have witnessed spells of scorching heat since March — usually a time of pleasant spring temperatures before the summer sets in, in mid-April. Delhi recorded a high of 40.1ºC, its hottest March temperature in nearly 75 years.
Temperatures across northern, eastern and central parts of the country hovered around 45ºC on Thursday.
A heatwave is declared when temperatures cross 40ºC or reach 4.5 degrees above the average for the time of year.
The Met office predicted extremely high temperatures in more than a dozen states over the next few days, including in Uttar Pradesh, Rajasthan, Haryana, Delhi, Punjab, Madhya Pradesh and Himachal Pradesh, and the union territory of Jammu.
People have been advised to avoid direct heat exposure, wear light clothing and cover their heads with a hat or umbrella.
In Agra, home of the Taj Mahal, the city's streets were deserted on Friday and many people sought relief from the heat in streams and ponds.
In West Bengal, authorities ordered schools to stock up on oral hydration salts for pupils.
In neighbouring Odisha state, the government closed schools and issued a “yellow warning” in 11 districts.
The intense heat caused a fire at one of Delhi's biggest rubbish dumps, as well as a forest fire in Uttarakhand's Srinagar district. Firefighters were battling the blaze in Delhi for a third day on Friday.
“We can say this is the hottest April since 2010 and is rare,” said Mahesh Palawat, vice president at private forecaster Skymet Weather, who attributed the unusual heat to “climate change and global warming".
“Extreme weather events are on rise. Prolonged heatwaves and long dry spells are now the norm,” Mr Palawat told The National.
He expected some relief by the second week of May.
The ordeal for residents of affected areas has been exacerbated by widespread electricity cuts, caused by heavy demand and a shortage of coal to run thermal power plants.
Peak power demand in the country of 1.3 billion reached a record 204.65 gigawatts on Thursday, the electricity ministry said, and is projected to increase to 215GW in coming months.
The federal government has cancelled several passenger trains to allow faster movement of coal carriages to replenish depleting inventories at power stations.
The government in the capital region said on Friday that the power shortage could affect Delhi's essential services, including metro trains and hospitals.