BBC:
For several weeks now, the Indian capital, Delhi, has been battling a severe heatwave, with temperatures routinely rising above 40C. The real feel, the weather apps helpfully tell us, is always a few degrees higher. But how hot do you feel when you hit the streets?
On Tuesday, the Indian Meteorological Department (IMD) recorded the maximum day temperature at 43.5C in the capital.
But we spent the day out on the city streets with a thermal camera deployed by Greenpeace India which recorded surface temperatures of up to 64C in some places.
The comparison is not like-for-like. The IMD’s official data reflects the temperature of the city air measured under standard conditions, while thermal cameras record the temperature of surfaces.
On hot days, roads, concrete, vehicles and other exposed surfaces can become substantially hotter than the air around them.
High surface temperatures increase the heat absorbed by the human body through radiation and can make urban areas feel considerably hotter than the official temperature, particularly where there is little shade or vegetation.
Our first stop was just after mid-day at the IIT flyover in south Delhi, one of the busiest traffic junctions in the city. Hundreds of thousands of vehicles pass this crossing daily and, in peak traffic, wait time can sometimes stretch up to 10 minutes.
As Greenpeace researcher Nibedita Saha moved her camera from the shaded areas under the flyover (where the reading was 42C) to the bikers idling at stop signals under the direct sunlight, the reading went up to 64C. The surface temperature of the spot where we stood was 61C – it fell to 39.8C when we moved less than 10ft away to stand under a tree.
