The National Weather Service developed the
heat index to help people identify days when the risk
for a heat illness is higher than normal. During a heat wave, the heat index is
excessive for many days in a row. Everyone has an increased risk for a
heat-related illness during a heat wave.
A heat-related illness can be more serious for:
Older adults, who may not notice excessive heat,
do not sweat as effectively, or do not feel thirsty.