MUNDANE MYSTERIES: How is “heat index” calculated?

Thermometer in front of cars and traffic during heatwave in Montreal.

MUNDANE MYSTERIES: How is “heat index” calculated?

As we enter into this mini end of summer heat wave you’ve probably heard the term “Heat Index” a lot the last few days. But how do the weather services actually calculate it?

They actually use a Heat index chart. All you need to find out what the heat index number will be is the temperature outside and the relative humidity percentage. For example, if the air temperature is 100°F and the relative humidity is 55%, the heat index will be 124°F. Hopefully we don’t get that high this week!

What is the heat index?

Via National Weather Service


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