Research has shown that the average annual temperature of cities with more than one million people can be 1º C to 12º C higher than that of surrounding areas.

This increase is due to the fact that the concrete, brick and asphalt that cover urban areas absorb heat from the sun during the day and reject it during the night. Urban structures can also increase absorption and reflection of the sun’s rays in addition to reducing air circulation.

On the other hand, buildings, cars and machinery found in cities can make the situation worse by releasing residual heat. Global warming and population growth are other factors that are increasing the effect of urban heat islands.