Why do they say it's 98 degrees outside and the heat index is 108?

Question

If it feels like 108 shouldn't they just say the temperature is 108. By the way, this is really happening today in Atlanta. Too hot to breathe.

Answer 1

The Heat Index is the measure of the Warm/Moist Air Parcel. The temperature is just the measure of the warm air parcel.

Typically however, your body can feel both the moisture in the air and the actual warm air by itself, which is why they have the heat index. Although in reality, the temp is much less not equating the moisture along with the warm air parcel.

Answer 2

The temp is what the thermometer says. The heat index is also know as the "feels like" temp. They don't say it's 108 outside because it actually isn't 108, it's 98. It just feels like it's 108! Stupid, yeah, but read this from Wikipedia:

The Heat index (HI) is an index that combines air temperature and relative humidity to determine an apparent temperature — how hot it actually feels. The human body normally cools itself by perspiration, or sweating, in which the water in the sweat evaporates and carries heat away from the body. However, when the relative humidity is high, the evaporation rate of water is reduced. This means heat is removed from the body at a lower rate, causing it to retain more heat than it would in dry air. Measurements have been taken based on subjective descriptions of how hot subjects feel for a given temperature and humidity, allowing an index to be made which corresponds a temperature and humidity combination to a higher temperature in dry air.

Answer 3

The heat index is like a counterpart to the wind chill. Both measurements are related to the rate at which heat leaves the body under given weather conditions.

The heat index increases with humidity, because humidity prevents sweat from evaporating, trapping heat in the body. The heat index is the temperature at which, in dry air, heat would leave the body at the same rate as it does at the actual temperature and relative humidity.

The wind chill is lowered by wind, because cold air in motion removes heat more efficiently than still air, removing heat from the body. The wind chill is the temperature at which, in still air, heat would leave the body at the same rate as it does at the actual temperature and wind speed.

Answer 4

the actually temperature is 98, but it feels like 108 because of the humidity