temperature-humidity index

(′tem·prə·chər hyü′mid·ədē ′in′deks)

(meteorology) An index which gives a numerical value, in the general range of 70-80, reflecting outdoor atmospheric conditions of temperature and humidity as a measure of comfort (or discomfort) during the warm season of the year; equal to 15 plus 0.4 times the sum of the dry-bulb and wet-bulb temperatures in degrees Fahrenheit. Also known as comfort index; discomfort index. Abbreviated CI; DI; THI.

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An arbitrary index that indicates the suitability of environmental conditions for physical activity. It is expressed as an equation:

comfort index = T+RH/4

where T is temperature in degrees Fahrenheit and RH is the relative humidity. When the comfort index is above 95 and the wind speed is low, it may be necessary to acclimatize to the conditions before attempting very strenuous activity; the presence of wind allows higher values to be tolerated.

An arbitrary index of the suitability of environmental conditions to physical activity. Comfort Index = (temperature + relative humidity)/4. Since the index was devised in the USA, temperature is measured in degrees Fahrenheit. A comfort index above 95 during low wind-speeds may require acclimatization; the presence of wind allows higher values to be tolerated.