Is the Temperature Humidity Index (THI) the same as dew point?

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Dear Tom,
Many years ago meteorologists referred to the “THI”, Temperature Humidity Index. Is the THI the same as the dew point?
Thanks, Joe Traxler
Dear Joe,
The National Weather Service began to use the THI to quantify discomfort from heat and humidity in the 1960s. The formula used temperature and dew point to derive an index that gauged discomfort. An index of 70 or lower meant that everyone was considered to be comfortable. At 71, 10% of the populace was deemed uncomfortable, 50% at 75 and 100% at 80. When the THI reached 84, government workers in non-air conditioned offices were sent home. The dew point was a part of the THI computation, but it was not the same thing. The dew point is a direct measure of the atmospheric moisture and equals the temperature at which air that is cooled becomes saturated (100 percent relative humidity).


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