[...]
In the countryside, vegetation uses sunlight and water from the soil for photosynthesis which in addition to converting carbon dioxide into oxygen, also releases water into the air.
This helps disperse solar energy and cool the surrounding area.
Meanwhile, in cities, there is not nearly as much vegetation to disperse heat.
Moreover, asphalt and cement absorb solar energy during the day and release it during the night.
The result is the city is hotter than the surrounding countryside, as buildings and streets act as a giant heat sink, and this is most noticeable during heatwaves.
[...]
To the list of factors making cities feel like ovens, there is another one which must be added: air conditioning.
"The more you use air conditioning in buildings, the more you heat the outside air," noted [Aude Lemonsu, who heads up Meteo-France's research centre.]
[...]
Paris and the central French city of Lyon have created maps showing where people can escape the heat, like air-conditioned museums and pools.
[...]