Created By : Naaz Fatima

Reviewed By : Phani Ponnapalli

Last Updated : May 08, 2023

The Heat Index Calculator is a useful tool that calculates the heat index value from other input data including temperature, relative humidity, and dew point. The tool is simple to use and provides you with the needed heat index in seconds.

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Relative Humidity:

What is the Heat Index?

The "felt air temperature" is measured by the heat index, also known as the humidex. To express how hot it actually feels, it takes into account both the air temperature and humidity. Because sweat evaporation, our natural cooling mechanism, is hampered by moist air, it feels hotter.

It's important to note that the heat index only takes into account relative humidity in shaded areas. As a result, the genuine heat index in full sunshine may be higher than the heat index calculator's estimate.

Heat Index Formula

The Heat Index Formula is based on two major variables: relative humidity and air temperature, with the variables remaining constant. Calculating the heat index manually requires a lot of computations. If that's the case, use our Heat Index Calculator to quickly find it. The following is the formula for calculating Heat Index

Heat Index (HI) = c1 + c2T + c3R + c4TR + c5T² + c6R² + c7T²R + c8TR² + c9T²R²

  • Where, HI = Heat Index
  • T = ambient Temperature in Fahrenheit
  • R = Relative Humidity
  • c1 – c9 = constants

Heat Index Chart

R.G Steadman devised the Heat Index, which took over 20 elements into account. You can use the Heat Index Chart below as a guide and make your own estimates to determine how hot it is outside. The provided Heat Index Chart is accurate enough to inform you of adverse weather circumstances such as heatstroke-causing temperatures, and so on.

How to Calculate Heat Index?

The heat index can be calculated using the temperature and either the relative humidity or the dew point. For further information on these factors, use the dew point calculator.

  • Step 1: Take a temperature reading outside. We're guessing it's around 95°F.
  • Step 2: Calculate the relative humidity, often known as the dew point. We'll assume that the relative humidity is 75% in this case.
  • Step 3: Fill in the blanks in the heat index calculator.
  • Step 4: Today's heat index is around 128°F.

Is the temperature indicated by the Heat Index correctly?

You might be surprised, but not in the way you think. R.G Steadman devised the heat index, which took into account roughly 20 parameters. for example, They included, walking pace, a person's height and weight, as well as wind speed, latitude (and thus the angle of the sun's rays), and even the pressure drop caused by altitude.

All of these components were presumed to be constant when the heat index calculation was simplified to simply two parameters. Your perceived temperature may differ from the one reported by our calculator if you walk faster than 1.4 m/s or if you are trekking high in the mountains. Nonetheless, it's precise enough to alert you when the temperature is hot enough to induce heatstroke.

FAQs on Heat Index

1. What factors affect the heat index?

Temperature and relative humidity are the two parameters that determine the heat index. It is used to calculate the overall effects of both of these elements on the felt temperature, based on assumptions about the human body, physical activity, and sun exposure.

2. What method do I use to calculate the Heat Index?

To calculate the heat index, do the following:

  • Step 1: Determine the temperature.
  • Step 2:Make a note of the relative humidity.
  • Step 3:Trace the relative humidity horizontally on the NOAA data graphic until it meets the temperature line. The heat index is the point where the two lines cross.

3. What is the value of the Heat Index?

The Heat Index is a determined temperature measurement that indicates how hot it feels based on the air temperature and moisture content.

4. Is the Heat Index Reliable?

The Heat Index is accurate enough that you can foresee terrible weather and avoid heatstroke.

5. What exactly is the Heat Index?

The Heat Index is a thermodynamic metric that takes into account both air temperature and relative humidity.