The mercury breached 45 degrees Celsius at 19 places in Rajasthan.
The weather department has issued a severe heatwave warning for northwest India during the next five days, and heat wave conditions will persist over central and east India over the next three days.
Warm winds and high temperatures have swept north India. Delhi's Najafgarh was the warmest place in the country after 47.6 degrees Celsius was recorded yesterday.
Rajasthan, Punjab and Haryana are marked in red in the India Meteorological Department's alert, asking people and authorities to take action. Meanwhile, parts of eastern Rajasthan and western Uttar Pradesh are in orange and people have been advised to stay alert and be prepared for high temperatures.
The mercury breached 45 degrees Celsius at 19 places in Rajasthan, 18 in Haryana, eight in Delhi and two in Punjab.
The threshold for a heat wave is met when the maximum temperature of a weather station reaches at least 40 degrees Celsius in the plains, 37 degrees in the coastal areas, and 30 degrees in the hilly regions, and the departure from normal is at least 4.5 notches.
A severe heat wave is declared if the departure from normal exceeds 6.4 notches.
The temperature is expected to stay in the normal range in Jammu and Kashmir, Ladakh and Himachal Pradesh. Hot and humid conditions are expected in Uttarakhand.
Meanwhile, in southern India, a heavy to heavy rainfall alert has been issued till the 23rd, with extremely heavy falls during 19-21 May.
The weather office said the southwest monsoon is very likely to advance into the south Andaman Sea, some parts of the Southeast Bay of Bengal and Nicobar Islands around May 19.
On Wednesday, a group of leading climate scientists said similar heat waves could occur once every 30 years, and these have already become about 45 times more likely due to climate change.
The scientists from the World Weather Attribution group emphasised that heat waves intensified by climate change are making life much tougher for people living in poverty across Asia.
The IMD had earlier warned of extreme heat in India during the April-June period, coinciding with the seven-phase Lok Sabha elections that end on June 1.