What is the heat index based on?

The heat index is based on temperature and humidity. It represents the apparent temperature, which is how hot it actually feels when relative humidity is factored in with the air temperature. This measurement is important because high humidity can impede the body's ability to cool itself through the evaporation of sweat, making it feel hotter than the actual air temperature.

When the humidity is high, sweat does not evaporate as efficiently, leading to increased body temperature and a higher risk of heat-related illnesses. Therefore, the heat index combines these two critical factors—temperature and humidity—to provide a more accurate understanding of the heat conditions in an environment. This is particularly relevant for safety assessments during hot weather, where monitoring both components can help guide safety measures and ensure that individuals are adequately protected from heat stress.