"Could be due to error," says IMD as Delhi's Mungeshpur AWS records whopping 52.9°C temperature

It was a calm summer afternoon in Delhi, when an abnormally high temperature reading at an Automatic Weather Stations (AWS) set the alarm bells ringing across the India Meteorological Department (IMD) offices at the national capital Delhi.

On Wednesday, an AWS at the Mungeshpur recorded all-time high temperature for Delhi at 52.9°C. This was surprising because of two main reasons. One, such high temperatures have never been witnessed in or around Delhi over the last 150 years of recorded history. Two, Wednesday's temperatures across the rest of Delhi NCR ranged from 45 to 49°C, with light rains reported in several places.

Like most of India, May is the hottest month for Delhi. But day's maximum temperatures rarely cross 48°C even on hottest of days in the recorded history. And mercury levels above 50°C is limited only to the western parts of Rajasthan in India.

By evening, IMD clarified that the reported abnormally high daytime maximum temperature at Mungeshpur was due to either an error or some local factor. AWS data is often not as reliable as IMD's five major observatories at Safdarjung, Palam, Ayanagar, Ridge and Lodi Road. Temperature over particular parts of a city could also vary due to local factors like land cover or human activities.

"The maximum temperature over Delhi NCR varied from 45.2° to 49.1°C in different parts of city, Mungeshpur reported 52.9°C 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," said IMD in a statement at 8 pm.

Earlier, Union Minister of Earth Sciences Kiren Rijiju highlighted the anomaly in a post on X, stating that the temperature of 52+ degrees Celsius in Delhi is "very unlikely."

The IMD further said that heatwave conditions are expected to decrease in the coming days. Light rains on Wednesday afternoon at several places across the city also caused temperatures to drop slightly.

"Heatwave conditions will reduce during the next 2 - 3 days due to gradual fall in temperature in association with approaching western disturbance, rainfall/thunderstorm and southwesterly wind blowing from the Arabian Sea to northwest India," the IMD release stated.

The IMD predicts a gradual decrease in maximum temperatures by 3-4 degrees Celsius over Northwest and Central India in the next three to four days.

As per the IMD records, the record all-time high temperature for Delhi is officially recorded at the Palam station on May 26, 1998, at 48.4°C. The record at its Safdarjung station remains 47.2°C recorded on May 29, 1944 — eight decades ago on the same day.

Across India, Rajasthan's Phalodi holds the record for highest-ever temperature at 51°C recorded on May 19, 2016. The years 2015 and 2016 witnessed many temperature records shatter due to strong El Niño over the Pacific Ocean, which is usually associated with warmer-than-normal temperatures across the Indian subcontinent. Fortunately, this year, the super-strong El Niño of 2023-24 dissipated just before the peak of Indian summers in April.

Though the abnormally high temperature recorded in Delhi could be a glitch, the growing heat stress in Indian cities is no longer an anomaly. 2023 was the warmest year on record, and the 10 warmest years in the 174-year global records have all occurred during the last decade (2014–2023). The cascading impacts of climate change mean that we will continue to witness several temperature records shatter every single year.