The weather department issued an orange alert for dangerously high temperatures in three states, West Bengal, Bihar and Andhra Pradesh, and said heatwave conditions are likely in parts of four others — Sikkim, Jharkhand, Odisha and Uttar Pradesh — as what might be a tougher summer than usual began taking hold across the country.
Some parts of India will, however, get some respite when a western disturbance brings thunderstorms to Jammu and Kashmir, Himachal Pradesh and Punjab on Tuesday, the India Meteorological Department said in its forecast.
Punjab and Haryana had heatwave-like temperatures on Monday, with similar conditions expected on Tuesday.
An orange alert for heatwaves implies high temperatures with increased likelihood of heat illnesses in people who are either exposed to sun for a prolonged period or doing heavy work. The alerts come a day after 13 people died at a Maharashtra government event while sitting in the open for several hours.
At particular risk during severe heat are vulnerable people, including infants, those of old age, and people with chronic diseases. IMD has recommended various preventive measures such as drinking sufficient water (even if not thirsty), drinking ORS (oral rehydration solutions or electrolyte replenishments) or similar homemade drinks to keep hydrated.
“When the winds blow from the eastern side or from the direction of Bay of Bengal then there is some clouding at times which bring down temperatures over the eastern states. But hot, dry winds from the northwest are blowing over east India, which has comparatively higher humidity levels due to their location. So, people in the eastern states need to take heat prevention measures adequately,” said M Mohapatra, director general, IMD.
What really makes the heat wave conditions severe is humidity and not temperature alone, Mohapatra added. “In coastal states, humidity is relatively high compared to the northern states, say Uttar Pradesh or other parts of northwest India even though the maximum temperatures are in a similar range. This is why we are also providing forecasts for humidity from this season,” Mohapatra added.
Humidity limits the ability of people to cool down because sweat does not evaporate as easily when the air is relatively moist. Such temperatures are also represented by what is known as a high wet bulb temperature. IMD does not provide wet bulb temperatures.
“Temperatures are very high over east India but humidity is still relatively low compared to June and July and because winds are from the northwest direction. Still the relative humidity levels we are seeing can also lead to discomfort and heat stress. They can be severe or fatal from when winds approaching from the east and similar temperatures prevail,” said Mahesh Palawat, vice president, climate and meteorology at Skymet Weather.
For instance, the maximum temperature at Asansol was 43°C with relative humidity of 47% at 8.30am; Angul recorded 43.1°C with RH of 74% at 8.30am and Bolangir recorded 43°C with RH of 78%. Kolkata recorded a maximum of 41.6°C with RH of 52% at 8.30am.
“These are high humidity levels but they would have reduced when maximum temperatures were recorded hence they are still bearable,” added Palawat. Even high-altitude regions such as Sikkim recorded heat wave conditions.
Heat wave conditions are considered when the maximum is over 40°C over the plains; over 37°C over coastal areas and over 30°C over hilly regions and the deviation from normal is between 4.5 and 6.4°C above the average maximum. If these conditions persist for two consecutive days, a heat wave is declared on the second day.
Experts also said that this year’s weather is unfolding in a kind of unusual manner that has become worryingly common — the changes are drastic — like it did in 2022 when much of the country skipped spring to go virtually straight from winter to summer.
“There is a clear change in weather pattern with snow season extending till first week of April and then sudden increase in temperature by mid-April,” said Sandeepan Mukherjee, a weather scientist at GB Pant National Institute of Himalayan Environment and Sustainable Development in Almora, speaking of how the trend has manifested in the Himalayan ranges.
On Sunday, maximum temperatures were in the range of 40-42°C over some parts of plains of northwest India, central and east India and 35-40°C over many parts of rest of the country except over Western Himalayan Region where it was 22-25°C.
Maximum temperatures were above normal by 3-5 degrees C in many parts of east and northeast India. Heat wave conditions have been recorded at a stretch in isolated pockets over Gangetic West Bengal for the last six days; coastal Andhra Pradesh for four days and Bihar for three days.
On Monday, the hottest places in India included Jayashankar Bhupalpalli district in Telangana, which recorded maximum of 44.6 degrees, Sultanpur in Uttar Pradesh, which recorded 43.4 degree Celsius, and Supaul in Bihar with 42.4 degree Celsius. Prayagraj, Jhansi, Kanpur, and Agra in UP, Patna and East Champaran in Bihar and Bathinda in Punjab recorded above 40 degree Celsius temperature.
The Bengal and Odisha administrations ordered schools to be shut on Monday, and the government of Tripura moved to early morning classes in order to mitigate the risks to children.
IMD’s heatwave warning covers 18 districts of Bengal. State chief minister Mamata Banerjee said she “has never seen such a heat wave in April”, and advised people to remain indoors between noon and 4pm.