Intense heat, warm nights with no respite: What's driving the extreme heatwave in India

While sunset usually brings some relief, this year, the night time temperatures also remain high.

An intense spell of heat continues to grip India, with the national capital sweltering and temperatures near the 45 degrees Celsius mark. The India Meteorological Department (IMD) has issued a heatwave alert that remains active for northwest and central India.

An orange alert remains active for large parts of northwest and central India for heatwave conditions (Keshav Singh/HT)

While India experiences extreme heat every year during April and May, this year the heat seems worse than before. Meteorologists say the current spell is being intensified by a combination of persistent dry weather, delayed western disturbances and a long-term rise in average temperatures.

While sunset usually brings some relief, this year, the temperatures remain high, with IMD reporting 31.9 as the minimum temperature at Delhi's Safdarjung station.

What is behind the heatwave in India?

According to IMD officials, one of the key reasons behind the ongoing heatwave is the absence of strong weather systems that typically bring cloud cover, rainfall or thunderstorms during the pre-monsoon period.

“We are not expecting any weather system to bring rain immediately. We can expect severe, large-scale heat waves over Uttar Pradesh. Over surrounding areas also we can expect scattered heat waves. People should be prepared and take necessary precautions,” IMD director general M Mohapatra had said earlier.

Northwest and central India naturally experience extreme heat during late April and May because of intense solar radiation, dry continental winds and low soil moisture. However, meteorologists note that this year’s prolonged dry spell has prevented any meaningful cooling.

Another major concern this year has been unusually high nighttime temperatures. Even after sunset, temperatures have remained elevated across several regions. Delhi’s Safdarjung station, for instance, recorded a minimum temperature of 31.9 degrees Celsius — far above the seasonal average.

Warm nights are particularly dangerous during heatwaves because they reduce the body’s ability to recover from daytime heat stress.

Why are nights remaining hotter than usual?

Weather experts say the elevated nighttime temperatures are being driven by a mix of regional weather conditions and long-term warming trends.

In cities, the urban heat island effect worsens nighttime heat retention. Dense infrastructure such as concrete buildings, asphalt roads and reduced green cover absorb heat through the day and slowly release it after sunset, keeping urban areas warmer than nearby rural regions.

However, scientists note that urban heat islands alone do not explain the widespread rise in nighttime temperatures across northwest India. Persistent dry air, weak winds and the lack of cloud-bearing weather systems have also contributed to poor nighttime cooling across a much larger region.

India has also witnessed a steady rise in average temperatures over recent decades. According to IMD climate data, the country’s average temperature has risen by around 0.7 degrees Celsius between 1901 and 2018, broadly consistent with global warming trends linked to rising greenhouse gas emissions.

Climate scientists have repeatedly warned that global warming is increasing the frequency, duration and intensity of heatwaves across South Asia. Studies published in recent years have shown that human-driven climate change has made extreme heat events more likely and more severe.

El Niño not yet active, El Niño–Southern Oscillation (ENSO) remains neutral

Although global climate agencies have forecast a possibility of El Niño developing later in the year, meteorologists say it is not responsible for the current heatwave conditions.

The US National Oceanic and Atmospheric Administration (NOAA) has projected a higher probability of El Niño conditions emerging during the monsoon season, between June and August. At present, however, El Niño–Southern Oscillation (ENSO) conditions remain neutral.

Similarly, IMD’s forecast of below-normal monsoon rainfall — estimated at 92% of the long-period average — relates to the broader June-September monsoon outlook and not directly to the ongoing May heatwave.

IMD warns of large-scale heatwaves

The IMD has predicted large-scale heatwaves across northwest and central India. Heat wave conditions are expected to prevail over Jammu-Kashmir-Ladakh and central Maharashtra on Monday and Tuesday; Punjab, Haryana, Chandigarh, Delhi and Madhya Pradesh until May 24, HT reported earlier.

“We are not expecting any weather system to bring rain immediately. We can expect severe, large-scale heat waves over Uttar Pradesh. Over surrounding areas also we can expect scattered heat waves. People should be prepared and take necessary precautions,” said M Mohapatra, director general, IMD.

An orange alert remains active for large parts of northwest and central India.