This weather station reported 52.9 degree Celsius today, the highest ever in India. Dr Mohapatra said there are 20 monitoring stations in Delhi and of these, 14 have recorded a drop in temperature and the average seen across Delhi was in the range of 45-50 degree Celsius.

He said the Mungeshpur station is an "outlier", and the recording needs to be confirmed. Some observatories in Delhi had shown a slightly higher temperature, but the Mungeshpur recording needs a full investigation.

A team of specialists has gone to Mungeshpur to check the temperature sensor, said Dr Mohapatra. He also speculated it could be local factors around Mungeshpur that could be the cause for this high recording.

"The maximum temperature over Delhi NCR varied from 45.2 to 49.1 degree Celsius in different parts of the city. Mungeshpur reported 52.9 degree Celsius as an outlier compared to other stations. It could be due to error in the sensor or the local factor. IMD is examining the data and sensors," the IMD said in a statement later this evening.

Earth Sciences Minister Kiren Rijiju said, "It is not official yet. Temperature of 52.3 degree Celsius in Delhi is very unlikely. Our senior officials in IMD have been asked to verify the news report. The official position will be stated soon."

Explaining the reason behind the rising temperature, India Meteorological Department (IMD) regional head Kuldeep Srivastava said the city's outskirts are the first areas to be hit by hot winds from Rajasthan.

"Parts of Delhi are particularly susceptible to the early arrival of these hot winds, worsening the already severe weather. Areas like Mungeshpur, Narela and Najafgarh are the first to experience the full force of these hot winds," he told news agency PTI.

The temperature was more than nine degrees higher than expected, the second day of record-breaking heat, and pushed up the mercury by more than degree from the 2002 record of 49.2 degree Celsius.

It also rained in Delhi briefly on Wednesday evening, which is likely to raise the humidity level.

Delhi's primary weather station Safdarjung observatory recorded a maximum temperature of 46.8 degree Celsius, highest in 79 years.

The IMD issued a red alert health notice for Delhi, with an estimated population of more than 30 million people. The alert warns there is a "very high likelihood of developing heat illness and heat stroke in all ages", with "extreme care needed for vulnerable people".

India is no stranger to searing summer temperatures, but years of scientific research have found climate change is causing heatwaves to become longer, more frequent and more intense.

The national capital reported its all-time high power demand of 8,302 megawatts (MW) amid the heatwave as more and more residents turned on power-intensive air-conditioning, electricity department officials said.

Other areas that reported extremely high temperature are both in the desert state Rajasthan - 51 degree Celsius in Phalodi, and 50.8 degree Celsius.

Sirsa in Haryana recorded 50.3 degree Celsius.

A fall of up to 4 degree Celsius over south Rajasthan districts - Barmer, Jodhpur, Udaipur, Sirohi, and Jalore - has been recorded today due to moist wind incursion from the Arabian Sea, indicating the beginning of the heatwave reduction over northwest India.

Numerical Weather Prediction (NWP) data, which uses computer models to process current weather observations to forecast future weather, are of the view that this decreasing trend would further extend northwards bringing gradual respite from heatwave conditions from May 30.

Also, incursion of moist winds from the Bay of Bengal from Thursday is likely to cause a gradual fall in maximum temperature over Uttar Pradesh.