Quick facts
- Humidity slows sweat evaporation, so the body sheds heat less efficiently.
- Direct sun, medication, age, outdoor work, and poor airflow can make risk higher than the number suggests.
- Use official heat alerts and local emergency guidance for action decisions.
Plain-English meaning
Heat index combines air temperature and humidity into a practical warning signal. It tries to answer a simple question: how hard is the environment making your body work to cool itself?
The number is useful because sweat only cools the body when it can evaporate. When air is humid, evaporation slows, so the body may keep gaining heat even if the thermometer number has not changed much.
Why it matters in the first hour
People often wait until they feel sick before changing plans. Heat index helps you act earlier: move into shade or air conditioning, slow down physical work, drink water, and check older adults, infants, outdoor workers, and people with chronic illness.
StormRift treats heat index as a decision trigger. If the index is high and cooling is limited, your first move is to reduce heat load before symptoms such as dizziness, confusion, or fainting develop.
What this page is not
This page explains the concept. It does not replace local alerts, medical advice, or emergency instructions. Use the linked heat survival guide for first-hour steps and the official sources for current safety guidance.
Sources and how they are used
- National Weather Service: Heat Safety Official safety source
- CDC: Heat and Health Official safety source
- Wikipedia: Heat index Background explainer