When Will the Heat End?

Dangerous heat is continuing to expand east this week, delivering the hottest temperatures of the year for many states in the South outside of Texas.

“The full wrath of summer is set to take hold of the South this weekend,” forecasters in Atlanta warned on Wednesday.

More than a dozen daily high-temperature records could be broken across the region through the end of the week. But what is even more dangerous is the record-breaking potential for what’s known as the high minimum temperature, which means locations are not expected to see much relief at night.

These high nighttime temperatures occur because the humidity keeps the air from cooling as efficiently at night. Humid air can also keep the body from cooling as efficiently because the air is so saturated that moisture from a person’s skin has nowhere to evaporate, a necessity for cooling down. This is why the heat index, which accounts for the combination of temperature and humidity, is an important measure of what the actual temperature feels like.

The highest heat index values of 110 to 120 over the next several days are expected to affect people in the cities of Dallas, Houston, Jackson, Miss., Little Rock, Ark., Nashville and New Orleans.

But it isn’t just the South: The heat is also affecting people from the Southwest to across the Southern Plains.

As the dome of high pressure shifts east during the long July 4 weekend, some relief is expected. Parts of Texas, the Lower Mississippi Valley and the mid-South will see temperatures trend down to near normal values this weekend, forecasters said. However, hazardous heat will continue for those along the Gulf Coast, where humidity is expected to remain high.