Heatwaves in India get hotter & longer, now double of normal: What lies ahead

High altitude regions such as Himachal reported 12 heatwave days followed by Sikkim (11), J&K(6) and Uttarakhand (2).

Delhi - which is experiencing heatwave for the fifth consecutive day - will see no respite till June 19, the India Meteorological Department (IMD) has predicted.

However, Delhi alone is not braving the heat this summer.  According to IMD, India witnessed its longest spell of heatwave days this summer.

A report by Times of India stated that Odisha experienced the most extreme weather between March 1 and June 9. The state topped the chart by recording the highest number of such days (27), followed by western Rajasthan (23), Gangetic West Bengal (21 days), and Delhi, Haryana, Chandigarh and west UP (20 days each) during this period. According to the weather office, these numbers were over double of what these regions normally get in a year.

As per IMD, a heatwave day is when the maximum is at least 40 degrees Celsius and 4.5 degrees and more above normal temperature. The slow progress of the southwest Monsoon has been blamed for the extended heatwave. According to the data, 14 of 36 meteorological subdivisions in the country have recorded over 15 heatwave days. Eastern and northern parts of India are the worst hit.

No sign of relief for Delhi

The heatwave spell will continue in Delhi as the IMD predicted that the temperature is expected to range between 44 and 45 degrees till June 19. However, there are chances of thunderstorms, lightning, and light rain at isolated locations on Friday afternoon or evening. The department issued a yellow alert from June 16 to 19.

Pusa was the hottest station at 47.2 degrees in the national capital on Thursday. Safdarjung, the city’s base station, also recorded a maximum temperature at 44.8 degrees Celsius, five degrees above normal, according to Times of India.

The minimum temperature was 29.4 degrees Celsius, one degree above normal. The relative humidity oscillated between 15% and 58% while the heat index was 44.2 degrees Celsius.

No respite at cooler altitudes

High altitude regions such as Himachal reported 12 heatwave days followed by Sikkim (11), J&K(6) and Uttarakhand (2).

“IMD’s map shows a high number of heatwaves over India. This was expected and predicted in advance. In the year following an El Niño year (2023) we tend to get more heatwaves. That is due to favourable atmospheric circulation for heatwaves,” Madhavan Rajeevan, climate scientist and former secretary, ministry of earth sciences, told The Times of India.

He also attributed the longer spell to global warming. “We will tend to get more frequent, longer and stronger heat waves. We, therefore, need to be well prepared,” said Rajeevan.

When is a heatwave declared?
A heatwave is declared when the maximum temperature of a weather station is at least 40°C in the plains and at least 30°C in hilly regions, and it is 4.5 to 6.4°C above the normal temperature. If it’s 6.5° or more above normal, a severe heatwave is declared. The heatwave is automatically considered if the temperature touches 45°C and a severe heatwave is declared if it reaches 47°C. In coastal areas, a heatwave is declared if the maximum temperature is 37°C or more and departure is 4.5° or more above normal.

However, the criteria of declaring heatwaves is not the same in the other countries. "It is usually defined based on the temperature thresholds over a region in terms of actual temperature or its departure from normal," the Met department told TOI.

The weather office also predicted a similar situation for Gangetic West Bengal, Bihar, Jharkhand, north Chhattisgarh and Odisha till June 16. Himachal, Jammu, Uttarakhand, northwest MP and north Rajasthan will also experience a reduction in intensity after June 16.