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1 month ago Hm.
According to the National Weather Service, heat index is measured by inputting the air temperature with the relative humidity at a given time.
That number represents the “feels-like” temperature, and helps to determine whether the National Weather Service will issue weather alerts or advisories.
If you want to get out a calculator and figure out the heat index yourself, here is the formula, as published by Lans P. Rothfusz in 1990 (noaa.gov):
HI = -42.379 + 2.04901523*T + 10.14333127*RH - .22475541*T*RH - .00683783*T*T - .05481717*RH*RH + .00122874*T*T*RH + .00085282*T*RH*RH - .00000199*T*T*RH*RHIn this formula, HI represents the heat index, while T represents the temperature in degrees Fahrenheit. RH represents the relative humidity. There are other adjustments that can be made in specific situations, but for the sake of simplicity, NWS also provides this website to calculate the heat index (noaa.gov).
One of the limitations of the heat index is that it’s devised for shady conditions with light breezes. Exposure to full sunshine can increase heat index values substantially, according to NWS, as can strong winds. For sunny conditions, forecasters typically use the WetBulb Globe Temperature formula (weather.gov), which measures heat in direct sunlight. It takes into account not just temperature and humidity, but also wind speed, sun angle and cloud cover. Those interested in seeing the WBGT in action can use this calculator tool (weather.gov).
Just curious. I'm not seeking any resolution to anything other than my curiosity.
In Japan we felt so hot. Period. I often felt like I was able to feel the air pressure that I normally don't notice. But looking at the temperature and humidity, 2 figures commonly available from various weather forecast sources, I don't see much difference b/w Georgia, which some American refer to as a hot area. I don't say Georgian summer is cool but not as hot as Japan I feel.