What is the “feels-like temperature?”

Curious as what this buzz word that meteorologists use often actually means?
Curious as to what this meteorology buzz word actually means?
Curious as to what this meteorology buzz word actually means?(KBTX Weather)
Published: Jul. 10, 2022 at 4:01 PM CDT|Updated: Jul. 10, 2022 at 4:02 PM CDT
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BRYAN, Texas (KBTX) - The entire state of Texas is currently experiencing a dangerous heatwave. Temperatures are climbing to 105° - 110° across the state, and yet meteorologists often bring up how it feels a lot hotter. That term --- the “feels-like temperature”--- may seem like a way to sensationalize the heat even more, but it is an actual scientific term that meteorologists use often.

Looking for a video breakdown? Check out this explanation below.

The “feels-like temperature,” or heat index during the summertime, can be broken down by one word: sweat. When your body starts to heat up and gets too hot, it begins to sweat. Once that sweat evaporates off your body, it actually lowers your body temperature through something called evaporational cooling. Most think of evaporation as a process that starts when a liquid gets too hot, so said liquid evaporates into a gas. However, evaporation is actually a cooling process. When a liquid turns into a gas, it takes energy away from its surroundings. This makes the liquid warm enough to switch to the gas phase and lowers the temperature of the surroundings. So, when sweat evaporates off of your body... it cools your body down!

Meteorologists use the term “feels-like temperature” to describe this sweat-evaporation process, but with an added variable --- humidity. When the humidity of the atmosphere is high, the air is already full of moisture. The high amount of water in the air makes it harder for sweat to evaporate --- in turn making it harder for evaporational cooling to lower your body temperature.

This process when combined with the humidity in the air, makes the human body feel a lot warmer than it actually is! Hence the name, feels-like temperature.

Believe it or not, the heat index is measured in shady conditions and calm winds. If exposed to direct sunlight, the heat index can increase by nearly 10-15°.

The following is a formula used to derive the heat index from two different variables:

  • T (air temperature in °F)
  • R (relative humidity percentage)

Heat Index = -42.379 + 2.04901523T + 10.14333127R - 0.22475541TR - 6.83783 x 10-3T2 - 5.481717 x 10-2R2 + 1.22874 x 10-3T2R + 8.5282 x 10-4TR2 - 1.99 x 10-6T2R2

If the math is not for you, the heat index can be easily calculated using a table, like the one below.

Easy tool to find the heat index from both the temperature and relative humidity.
Easy tool to find the heat index from both the temperature and relative humidity.(National Weather Service)

If you know both the air temperature (°F) and relative humidity (%), this table will give you the feels-like temperature. The darker the red of the heat index, the more dangerous it becomes to stay in the heat for prolonged periods of time.

So yes... the feels-like temperature is a real scientific value. It accurately represents how your body is reacting to the heat.

In the wintertime, the feels-like temperature flips from the heat index to wind chill. With high winds and cold temperatures, the body is unable to warm up as quickly, making it feel a lot colder than the temperature reflected on the thermometer.

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