NEW YORK - JULY 10:  A man wipes sweat from his face July 10, 2007 in New York City. New York City is experiencing a second day of a heat wave with temperatures in the upper 90`s and uncomfortable humidity levels.  (Photo by Spencer Platt/Getty Images)
Nighttime 'lows' more dangerous than highs
01:07 - Source: CNN
CNN  — 

More than 20 million Americans across 16 states were under heat alerts Wednesday as cities across the country reported daily record-high temperatures, with the worst of the sweltering heat hitting the South and the Great Plains.

Atlanta, Georgia, tied its June 22 record with 98 degrees Fahrenheit Wednesday while about 80 miles south, Macon set a new heat record for the day with 105 degrees, according to the National Weather Service.

Zoo Atlanta announced on its website it would be closing early Wednesday and Thursday due to “extremely high heat indexes.” The care teams at the zoo will monitor and check on all animal habitats multiple times throughout the day to ensure their safety, zoo spokesperson Rachel Davis told CNN.

Nashville recorded its first day of 100 degrees for the first time in nearly a decade, according to the weather service. The city also broke its temperature record for the date of June 22, reporting 101 degrees shortly before 3 p.m., the service said.

At least a dozen high-temperature records were tied or broken across the Eastern US from Arkansas to the Carolinas – all the way to New York.

Volunteers cart water bottles and snacks to handout to residents at the Dr. Martin Luther King Jr. Community Center during a heatwave in Dallas, Texas,  on June 22, 2022.

One part of widespread extreme weather

It’s the second heat wave in as many weeks for many parts of the country. An enormous heat dome across the eastern US and the Midwest created record high temperatures in several cities last week. And other parts of the country faced extreme weather including historic flooding, wildfires and severe storms.

And there’s no relief in sight.

The heat in the South and the Plains is expected to continue to build over the coming days with much of the region expected to see more records, the service said.

About 65% of the US population will see temperatures above 90 degrees over the next week, and almost 55 million will be sweltering in temperatures at or above 100.

Officials in New Orleans have warned the heat index could be as high as 115 degrees this week, and the city has set up several cooling shelters.

The region was feeling the heat by Wednesday. By afternoon, Pascagoula and Slidell had both hit 100 degrees, while Baton Rouge and Gulfport thermometers were recording 98 degrees, the weather service in New Orleans said on Twitter.

At least five people died

At least five people died of heat-related causes last week – four in Georgia and one in Tennessee.

Power companies in the South surveyed by CNN earlier said they were prepared for this week’s heat wave.

“This is our ‘Super Bowl’ that we prepare all year for,” Tennessee Valley Authority (TVA) spokesperson Scott Fiedler said in a statement to CNN. “TVA is extremely well-positioned to meet power demand during this week’s hot weather. As you know, temperature and load go hand in hand. So we should see high loads the rest of this week.”

CNN’s Taylor Ward and Devon Sayers contributed to this report.