Question 1

What is the heat index?

Accepted Answer

The heat index combines air temperature and relative humidity to determine how hot it actually feels. High humidity reduces the effectiveness of sweating, making hot weather feel even hotter.

Question 2

At what heat index should I be concerned?

Accepted Answer

91-103°F: Extreme caution. 103-124°F: Danger. 125°F+: Extreme danger. Heat stroke is likely with prolonged exposure at 103°F+.

Question 3

Why does humidity make it feel hotter?

Accepted Answer

Humidity reduces evaporation of sweat from your skin. Since sweating is your body's primary cooling mechanism, high humidity makes it harder to cool down, causing heat to feel more intense.

Question 4

What is the difference between heat index and wet-bulb temperature?

Accepted Answer

Heat index estimates how hot it feels to humans in shade with light wind. Wet-bulb temperature measures the lowest temperature achievable by evaporative cooling and is a more direct measure of heat stress danger.

Heat Index Calculator

Heat Safety

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