Delhi’s Heatwave: Official Temperatures vs. Real Feel
For several weeks, Delhi has been enduring a severe heatwave, with temperatures frequently exceeding 40°C. Weather apps often report a "real feel" temperature a few degrees higher than the official readings. But how intense is the heat when experienced on the streets?
On Tuesday, the Indian Meteorological Department (IMD) recorded a maximum daytime temperature of 43.5°C in Delhi.
However, Greenpeace India deployed a thermal camera to measure surface temperatures across the city streets, recording readings as high as 64°C in certain locations.
The IMD’s official temperature reflects the air temperature measured under standardized conditions, whereas thermal cameras capture the temperature of surfaces. On hot days, surfaces such as roads, concrete, and vehicles can become significantly hotter than the surrounding air.
Elevated surface temperatures increase the heat absorbed by the human body through radiation, making urban areas feel much hotter than the official temperature, especially in places lacking shade or vegetation.
Heat at IIT Flyover: A Case Study
The first location visited was the IIT flyover in south Delhi, a major traffic junction with hundreds of thousands of vehicles passing daily. During peak traffic, wait times at signals can reach up to 10 minutes.
Greenpeace researcher Nibedita Saha used the thermal camera to compare shaded areas under the flyover, which registered 42°C, to bikers waiting at stop signals under direct sunlight, where temperatures reached 64°C. The surface temperature at the spot where the team stood was 61°C, but it dropped to 39.8°C just 10 feet away under a tree.
"Consistent exposure to such high temperatures can cause major health issues," said Nibedita, adding, "We got instant relief. That's the difference just one tree can make."
Health Risks of Extreme Heat
Dr. A Fathahudeen, a pulmonologist, explained that the human core body temperature is normally 37°C, but prolonged exposure to high heat can raise it.
"When it exceeds 40°C, the body ceases to work normally. The most common symptom is heat exhaustion. People become extremely sweaty, complain of headaches and fatigue," he said. "In more serious cases, people can become confused and dazed and even have seizures.
"If not treated urgently, they can have multiple organ failures, leading to death," he added.
To stay safe during heatwaves, Dr. Fathahudeen advised continuous hydration even without thirst, wearing loose and light-colored clothing, and using umbrellas. He also urged the government to issue advisories restricting outdoor labor between 10:30 am and 3 pm.
However, such precautions are often not feasible for Delhi’s poor.
Heat Impact on Street Vendors at Red Fort
At the Red Fort in Old Delhi, despite the intense heat, some shoppers, pilgrims, and tourists were present, and street vendors had set up their stalls hoping for customers.
Sanjana Ben, a dry fruit vendor sitting on the pavement with small sacks of cashews, almonds, raisins, walnuts, and dried figs, described her situation.
The thermal camera recorded approximately 40°C on her face, but temperatures rose to 51.4°C closer to the ground and reached 57°C just a few inches away.
"At times my head spins and my vision blurs. When the ground feels very hot, I stand up for a bit. But how long can I do that, so I sit down again," Sanjana Ben told the BBC.
Nearby, footwear vendor Mohammad Mahfouz Alam described the relentless heat.
"There's no relief day or night. I feel listless, my legs hurt. I reach home exhausted. Even after I take a bath, I cannot sleep. The fan blows hot air and I keep tossing and turning in bed."
He noted that the city’s weather has changed over the years, with seasons becoming more erratic and unpredictable, impacting those who live and work on the streets the most.
"If this tree wasn't there, it'll be impossible for me to be here. The day this tree is gone, everything will be over," he said, pointing to a tree providing shade near his stall.
As the camera focused on Mahfouz Alam and his surroundings, surface temperatures ranged from 40°C to 58.65°C, with his shoulder registering 44.8°C.
Chandni Chowk and Sundar Nagri: Heat in Dense Urban Areas
A short walk from the vendors’ stalls is Chandni Chowk, a bustling market stretching from the Red Fort to Fatehpuri Mosque, featuring narrow alleyways and numerous shops and food stalls.
The main boulevard was converted into a pedestrian zone with stone pillars installed on both sides to provide resting spots. However, due to lack of shade, these pillars remain unused.
A young plastic toy vendor was found sitting on a concrete pillar registering 56.9°C while engrossed on his phone.
Later, the team visited Sundar Nagri, a lower-middle-class neighborhood in east Delhi’s Seelampur area, around 5 pm as the sun’s intensity began to wane. Nonetheless, surfaces exposed to direct sunlight remained extremely hot, with a concrete bench at the colony’s entrance recording 51.6°C.
As the team walked through crowded street markets selling mangoes, clothes, footwear, and vegetables, a dust storm appeared on the horizon.
The small concrete homes in Sundar Nagri are closely packed, with narrow lanes barely wide enough for one person to pass.
For the past two weeks, siblings Abhishek and Kajal have been maintaining a "Garmi khata" (heat register) documenting how extreme heat affects their bodies, sleep, incomes, and daily lives for a Greenpeace project.
Outside their home, the thermal camera recorded 42°C. Inside their two-room home, temperatures hovered around 40°C, with little difference from outside.
The home had no windows or outlets for heat to escape, and a small ceiling fan circulated hot air.
"When it's very hot, I feel nauseous," Kajal said. "You can't go out, you can't stay in."
Abhishek read from his register:
"This week's heat has changed our daily routines. Everyone returns home late and no-one is sleeping well. In the mornings, the fan is switched off during cooking and the heat becomes unbearable. My sister finds it hard to do her chores. My mother looks more tired than ever."
"The days, he said, passed somehow, but the nights were most difficult. "I've cut my hair short, I get up several times to wash my face, I take off my t-shirt, but I still can't sleep at night. Outside, there's at least a breeze, inside it feels like I'm standing next to an oven."
