I have noticed increased emphasis on “heat index” in TV weather reporting.
I’m honestly getting tired of it, as “heat index” has become the focal point of sensationalist garbage in legacy media and on social media.
It’s not a measurable quantity and it has little scientific value. Its calculation relies on numerous assumptions:
You are 5 ft. 7 in. tall and weigh 147 pounds.
Your body is 84% covered in clothing (long trousers and a short-sleeved shirt), and those clothes are 20% fiber.
Your body temperature is a constant 98.6°F (37.0°C), and doesn’t change with outdoor air temperature.
You are walking, not sitting, and are moving at a forward velocity of 3.1 mph.
There is no wind blowing.
There are perfectly clear skies overhead, and no clouds.
There are no correction factors for the time of day (for sun angle), changes in the latitude, or culture (different clothing).
And there are many more assumptions.
It is true that humid air feels oppressive at the same temperature and pressure than comparatively dry air, but how hot it feels will differ from person to person.
If you’re a 300+ pound fat ass, a 95° day with a dew point of 78° will feel a lot hotter than it would to someone who is 160 pounds and in shape.
“Heat index” records also don’t go back very far, so there’s no way of knowing what the “heat index” might have been during some of our most historic heatwaves in the 1930s and 1950s. That is why we take actual measurements of air temperature two meters above the ground in a white, enclosed shelter with louvered sides to allow airflow.
Via: https://www.weather.gov/media/ffc/ta_htindx.PDF
