Sudden April heat spike leaves Delhi unprepared, doctors warn of rising risks

Most patients are presenting with severe dehydration, dizziness and heat exhaustion, said Dr Prashant Sinha, head of emergency at PSRI hospital.

While summers in north India normally build gradually, allowing the human body to adjust over weeks, the transition to extreme heat has been abrupt this year, leaving little room for biological adaptation and putting people at higher risk of heat-related illnesses, warned experts.

Heat arrives too soon, increasing risk of heatstroke and dehydration (Representative/Freepik)

“High temperatures arriving earlier than usual put a strain on the body’s ability to acclimatise to hot weather, a phenomenon called seasonal or heat acclimatisation,” said Dr Mugdha Tapdiya, director of internal medicine at Fortis Hospital, Vasant Kunj.

Under normal conditions, repeated exposure to heat over days or weeks triggers a series of physical responses: the body begins to sweat earlier and more efficiently, heart rate under heat stress reduces, and the system becomes better at maintaining fluid and electrolyte balance. This physiological adaptation, referred to as heat acclimatisation, typically takes about one to two weeks of progressive exposure.

“However, a sudden increase in temperature becomes more dangerous as the body’s natural acclimatisation has not properly started. The sudden spike is difficult for the body to tolerate and makes it harder to regulate temperature, leading to rapid dehydration and electrolyte loss. In these conditions, even healthy people become vulnerable to heat exhaustion and heatstroke,” said Dr Rajesh Rajan, chairman BOG, Indian Association of Clinical Cardiologists, and president, Association of MD Physicians.

There is also a behavioural aspect. “Many people have not yet shifted to summer routines such as increased fluid intake, lighter meals or adjusted outdoor schedules,” said Dr Manisha Arora, director of internal medicine at CK Birla Hospital.

This puts excessive strain on the body which can result in heatstroke, heart rhythm disturbances and other heat-related complications.

“Usually, hospitals start getting cases of heat exhaustion in late May and June, when the heatwave properly begins. Patients typically experience heavy sweating, dizziness, headache, nausea and muscle cramps. However, this year, cases have started appearing in April itself,” Rajan said.

Most patients are presenting with severe dehydration, dizziness and heat exhaustion, said Dr Prashant Sinha, head of emergency at PSRI hospital. “What makes this phase particularly risky is the body’s unpreparedness. April heat of this intensity leaves little time for physiological adjustment, increasing the likelihood of rapid deterioration.”

Experts said vulnerable groups, such as the elderly, children, outdoor workers and those with heart or kidney conditions, are at higher risk of heat-related ailments. “Children lose fluids faster, and their inability to clearly express discomfort often delays intervention,” said Dr Sanjay K Jain, HOD paediatrics and neonatology, and medical director at Maccure hospital.

How body can still adapt

Experts emphasise that much of the risk can still be mitigated if people consciously allow their bodies to adapt to the heat.

“The method is simple. Start with 20 to 30 minutes outdoors during cooler hours and increase duration gradually, with proper hydration,” said Tapdiya, adding that mitigation efforts need to move beyond individuals to institutions and employers.

“Employers can introduce graded shifts at the start of summer. RWAs can ensure shaded areas and water access. Schools can time outdoor activities safely rather than cancel them entirely. Heatwaves are predictable. Deaths from them are not inevitable. In a warming Delhi, survival will depend not just on escaping the heat but on learning how to live with it,” she said.

Ranjan recommended spending at least 30 minutes to an hour in a non-AC room or in a shaded area outside for about 20 minutes. “One should learn how to acclimatise by gradually getting used to heat, increasing fluid intake, avoiding the hottest hours of the day, and wearing appropriate clothing,” said Dr Sunil Rana, associate director and head of internal medicine at Asian Hospital.