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Heat index

UK //hiːt ˈɪndɛks// US //hit ˈɪndɛks// Pronunciation

Definition

A measure that combines air temperature and humidity to indicate perceived heat.

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In simple words: A number showing how hot it feels when humidity is added to the temperature.

Examples

• The heat index today is expected to be above 100 degrees, making it feel much hotter.
• During humid summer days, the heat index can be significantly higher than the actual temperature.
• It's important to check the heat index if you plan to spend time outdoors in high temperatures.
• The weather report mentioned a heat index warning due to the extreme humidity levels.
• Understanding the heat index can help prevent heat-related illnesses during hot weather.

Usage notes

Used primarily in weather reports and discussions about temperature; not commonly used in casual conversation.

Grammar pattern

standalone term

Memory hint

Think of it as 'heat + index' — measuring heat with humidity factored in.

Collocations

• calculate heat index
• monitor heat index
• high heat index
• heat index warning
• heat index value

Synonyms

• humidex
• heat stress index
• apparent temperature
• sensible heat
• thermal discomfort index

Common mistakes

• Confused with 'heat wave', which refers to a period of excessively hot weather.
• Using 'heat index' incorrectly to describe just temperature, without considering humidity.
• Believing that the heat index is always higher than the temperature, which is not necessarily true.