This index can be useful for calculating the dangers related to medical issues such as muscle cramping, dehydration, heat exhaustion, or the more serious heatstroke on hot and humid days. When relative humidity is high, it becomes increasingly difficult for the body's sweat to evaporate, leaving individuals without an effective natural way to cool off. Maps of heat advisories or warnings are often a product of reclassifying the heat index result into classes, where the higher the index value, the more likely it is to become a warning rather than just an advisory.