Heat wave frequency across core heat wave zone comprising Punjab, Haryana increased by 0.1 days per decade

BATHINDA: India’s heat crisis is becoming more relentless, more humid, and increasingly inescapable, stretching beyond scorching afternoons into dangerously warm nights. The past decade is increasingly showing a clear trend that country’s summers are becoming not just hotter, but more dangerous, finds a study by Climate Trends, a research based consultancy, released on Friday.


The study using IMD data finds that heat wave frequency across country’s core heat wave zone has increased by 0.1 days per decade (1961–2020), which means roughly one-tenth of a day more of heatwave condition. The duration of heatwaves across India’s heatwave-prone regions has increased by 0.44 days per decade. India’s average night-time temperatures are rising by approximately 0.21°C per decade.

The 35 states and union territories (UTs) show increasing nighttime warming trends as India’s average relative humidity increased from 67.1% to 71.2% between 2015–2019 and 2020–2024. Human-caused climate change is increasing baseline temperatures, so heatwaves start from a hotter background and reach higher peaks.


The core heatwave zone (CHZ) covers the states of Punjab, Haryana, Himachal Pradesh, Uttarakhand, Delhi, Rajasthan, Uttar Pradesh, Gujarat, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, West Bengal, Odisha and Telangana.


According to meteorologists, the ongoing weather conditions are due to the unabated flow of hot north-westerly winds coming from the desert region across Rajasthan, Punjab, Haryana, till the central India. Minimum temperatures have also been settling above average, further contributing to heat stress.

Most of the night temperatures have been settling in the late 20s, and some stations have also reached 30°C. According to the WHO Housing and Health Guidelines, indoor air temperatures should not consistently exceed 24°C to prevent heat-related health risks, cardiovascular strain, and autonomic disruption during sleep.


According to a study by IMD, there is an increasing trend of 0.1 days/decade in the frequency of heat waves averaged over the core heatwave zone (CHZ) during 1961-2020. Also, the total duration of heat waves averaged over the CHZ has increased by 0.44 days per decade, with the maximum duration showing an increasing trend of 0.55 days per decade. All the trends are statistically significant. Severe heatwaves have also seen an increasing trend in the frequency, total number, and maximum duration in the CHZ.


According to the World Meteorological Organization (WMO), 2025 was among the three warmest years ever recorded globally, with global temperatures reaching nearly 1.44°C above pre-industrial levels. The past eleven years, 2015-2025, are the eleven warmest years in all eight datasets.


“In the absence of any weather system over the Indian mainland, hot northwesterly winds from the desert of the adjoining Sindh region of Pakistan and Rajasthan are penetrating deep into the country. The uninterrupted flow of these winds for the last three to four days has been pushing the mercury, resulting in heatwave to severe heatwave conditions.

When the days are hot and there are no pre-Monsoon activities in the evening, these high temperatures are also reflected in higher nighttime temperatures. The ongoing weather conditions are considered to be the normal seasonal pattern during May, which is also the peak of the summer season. We would only see some respite, with the arrival of the western disturbance, which would then alter the wind pattern, bringing in much-needed relief,” said Mahesh Palawat, Vice President- Meteorology and Climate Change, Skymet Weather.


“India’s heatwaves are no longer being driven by temperature alone. What we are witnessing today is a dangerous convergence of rising temperatures, warmer nights, increasing humidity, and rapid urbanisation, all of which are amplifying heat stress across the country. Heat is becoming more prolonged, more humid, and increasingly difficult to escape, especially for vulnerable communities and outdoor workers.

These changing weather patterns are a stark reminder that climate change is now reshaping how heat is experienced in India, turning it into a major public health, economic, and development challenge,” said Aarti Khosla, Founder and Director, Climate Trends.