# Heat Index and Wind Chill

**URL:** <https://boards.straightdope.com/t/heat-index-and-wind-chill/215986>\
**Category:** Factual Questions\
**Created:** [November 29, 2003, 10:44pm UTC](https://boards.straightdope.com/t/heat-index-and-wind-chill/215986 "2003-11-29T22:44:26Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![gypsymoth3](https://avatars.discourse-cdn.com/v4/letter/g/85e7bf/32.png) [@gypsymoth3](https://boards.straightdope.com/u/gypsymoth3)\
**Post date:** [November 29, 2003, 10:44pm UTC](https://boards.straightdope.com/t/heat-index-and-wind-chill/215986/1 "2003-11-29T22:44:26Z")

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how come thermometers (like the ones at banks) cant’ detect heat index and wind chill? is it just because we have sweat and oils and stuff on us that evaporate and they don’t? and how do meteorologists measure heat index and wind chill if a regular thermometer can’t detect it? do they have some kind of special device or just a formula using wind speed, humidity, temperature, etc.?

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**Author:** ![Earthling](https://avatars.discourse-cdn.com/v4/letter/e/90db22/32.png) [@Earthling](https://boards.straightdope.com/u/Earthling)\
**Post date:** [November 29, 2003, 11:03pm UTC](https://boards.straightdope.com/t/heat-index-and-wind-chill/215986/2 "2003-11-29T23:03:01Z")

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I am not a meteorologist, but this is my understanding:

Temperature, humidity, and wind measurement each require separate instruments. Bank displays, evidently, have just one. And the heat or wind-chill indices are calculated as “equivalent” (or, “how it feels to you”) temperatures based on a temp + humidity (heat index) or temp + wind (wind-chill).

From _The Handy Weather Answer Book_ (Walter A Lyons, ©1997), on wind chill (pp. 205-206):

> [@](#):
>
> The windchill factor (or windchill index) is a number, often expressed as an equivalent temperature, that expresses the cooling effect of moving air at different temperatures. The lower the windchill, the more calories of heat are being carried away from the exposed surface of the body.

And on heat index (p. 241):

> [@](#):
>
> High humidities greatly reduce the ability of the body to coll itself by its own evaporative cooler – sweat.

If you wanted to spend the bucks, you can actually get your own [hand-held weather station](http://www.nkhome.com/ww/wwindex.html) that tells you all that info.