During heatwaves, the centers of the city are heated compared to the surrounding areas according to an average of 4-6C (39-43F). European Commission Joint Research Center, external,
The difference in extreme cases can be as much as 10C (50F), especially in very quiet weather to mix air.
One of the major causes of this contrast is hard, dark, dark surfaces like buildings and roads, dominating the urban landscape.
They absorb the sun’s energy instead of reflecting it, which means they store heat. It is then released gradually in the surrounding air, especially at night.
The air conditioning units, vehicles – and the waste heat generated by humans – add it even further.
