Heat index days are periods characterized by a combination of high air temperature and humidity, resulting in a perceived temperature that feels hotter than the actual air temperature. This phenomenon can lead to significant health risks, particularly during the summer months. The heat index, calculated using both air temperature and relative humidity, is a critical measure used by meteorologists to assess the potential impact of heat on human health. High humidity reduces the body's ability to cool itself through sweating, increasing the risk of heat-related illnesses such as dehydration, heat exhaustion, and heat stroke.