What is a heatwave?

• The India Meteorological Department (IMD) issued detailed heatwave guidance and advisories as several parts of the country continue to experience rising temperatures and above-normal conditions.

• As per the latest assessment, maximum temperatures in many parts of northwest, central and peninsular India are currently ranging between 40°C to 44°C.

• In several regions, temperatures have been observed to be markedly above normal by 5°C or more, indicating a developing heat stress scenario across parts of the country.

• The IMD has indicated that heatwave conditions are very likely to develop in isolated pockets of Jammu & Kashmir, Himachal Pradesh, Punjab, Haryana, Chandigarh & Delhi, Uttar Pradesh, Rajasthan and central India over the coming days. 

• At the same time, hot and humid conditions are expected over coastal and eastern regions, while warm night conditions are likely in parts of north India, which may further increase discomfort levels and health risks.

• India’s peak power demand hit an all-time high of 256.11 GW on April 25 due to an intensifying heatwave, which increased the use of cooling devices such as air conditioners and desert coolers, according to the latest power ministry data.

• The IMD’s extended outlook indicates that heatwave conditions are likely to persist across multiple regions over the next seven days, particularly in parts of:

i) Northwest India (Punjab, Haryana, Delhi, Rajasthan, Uttar Pradesh)

ii) Central India (Madhya Pradesh, Chhattisgarh, Vidarbha)

iii) Select southern regions (Kerala & Mahe).

• According to IMD’s seasonal outlook for April to June 2026, above-normal heatwave days are likely over parts of east, central and northwest India and the southeast peninsula, underscoring the need for continued preparedness and mitigation measures during the ongoing hot weather season.

What is a heatwave?

• Higher daily peak temperatures and longer, more intense heatwaves are becoming increasingly frequent globally due to climate change. 

• India too is feeling the impact of climate change in terms of increased instances of heatwaves which are more intense in nature with each passing year, and have a devastating impact on human health thereby increasing the number of heatwave casualties.

• Heatwaves do not fetch as much public attention as more dramatic disasters such as earthquakes and floods, but until more recently they were taking a substantial toll of lives in India.

• A heatwave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season. 

• Heatwaves typically occur between March and June, and in some rare cases even extend till July. 

• The extreme temperatures and resultant atmospheric conditions adversely affect people as they cause physiological stress, sometimes resulting in death.

The IMD has given the following criteria for heatwaves:

i) Heatwave is considered if maximum temperature of a station reaches at least 40°C or more for plains and at least 30°C or more for hilly regions.

ii) When normal maximum temperature of a station is less than or equal to 40°C heatwave departure from normal is 5°C to 6°C severe heatwave departure from normal is 7°C or more.

iii) When normal maximum temperature of a station is more than 40°C heatwave departure from normal is 4°C to 5°C severe heatwave departure from normal is 6°C or more.

iv) When actual maximum temperature remains 45°C or more irrespective of normal maximum temperature, heatwaves should be declared. 

• Heatwaves amplify many risks, such as health-related or economic risks, including increased human mortality, drought and water quality, wildfire and smoke, power shortages and agricultural losses.  

• The health impact of heatwaves typically involve dehydration, heat cramps, heat exhaustion and/or heat stroke.