The urban heat island effect makes it more difficult for humans to deal with heat waves. When temperatures are too high, people can suffer from heat exhaustion, but heat waves can also lead to increased mortality rates.

And since heat waves will become more severe and more frequent in the future, the urban heat island effect makes populations even more vulnerable to heat waves, and the risks of harm, both to human and animal health, are exponentially increased.

Children, seniors, pregnant individuals and people living with chronic conditions such as cardiovascular diseases, diabetes, and respiratory illnesses will experience increased negative effects due to heatwaves. 

The urban heat island effect also increases the energy demand and expenses from cooling buildings and homes. It increases stress on municipal systems, such as water distribution systems, since heat creates greater demand for water.

Urban heat islands are also more prone to smog formation, mainly from car exhaust. Trees and ecosystems usually filter pollutants from air. When these are absent, air quality is worsened.