Heat Safety
Heat Index vs Temperature: Why Humidity Makes Hot Weather More Dangerous
The difference between air temperature and heat index, why humidity matters, and how to use heat alerts for safer outdoor plans.
Quick answer: Heat index estimates how hot conditions feel to the body when humidity slows sweat evaporation and cooling.
Temperature alone
Air temperature tells you how warm the air is, but it does not fully describe how hard it is for the body to cool.
Sun, wind, clothing, pavement, and workload also matter.
Humidity effect
When humidity is high, sweat evaporates more slowly.
That means the body can overheat at lower air temperatures than people might expect.
Safety use
Use heat index, local heat alerts, shade, hydration, rest breaks, and acclimatization to plan outdoor time.
Heat illness can become serious quickly when symptoms are ignored.