CHICAGO — If the extreme heat and humidity lingering over much of the nation feels like a steam bath, it’s because the same principles are at work in the atmosphere.
Vast amounts of warmth and moisture have become trapped under a huge “heat dome,” bringing record-breaking temperatures and thick, topical air to scores of cities from North Dakota to the Ohio Valley.
What’s more, because of the humidity, even nighttime brings little relief. Humidity makes the weather feel far hotter because the body, which cools itself by perspiring, has to work harder when the air is already moist.
This difference is expressed by the heat index — a measure of humidity combined with temperature. On Tuesday, the heat dome produced some eye-popping heat index readings: 129 degrees in Newton, Iowa, 122 in Gwinner, N.D., and 121 in Taylorville, Ill.
For the full story, see Thursday's TH.