Urban heat islands cause higher temperatures in urban areas compared to surrounding rural areas due to heat retention by buildings and pavement. This increase in ambient temperature raises the risk of heat-related illnesses such as heatstroke, especially among vulnerable populations like the elderly and those with chronic diseases. Heatstroke occurs when the body’s thermoregulation fails under extreme heat stress, leading to life-threatening complications. Therefore, the primary health impact associated with urban heat islands is an increased risk of heatstroke.

Reference: Harrison’s Principles of Internal Medicine, Kasper et al., 21st Edition.