Millions of people across Alabama, Arkansas, Mississippi and Tennessee faced excessive heat warnings and high humidity.
A heat wave in the South forced residents to contend with scorching temperatures and dangerously high humidity on Monday and Tuesday.
Temperatures were expected to climb above 100 degrees in some places, with heat indexes as high as 118 degrees, the National Weather Service said on Tuesday.
“For 2019, this is definitely the hottest we’ve seen so far,” said Thomas Winesett, a meteorologist with the National Weather Service in Jackson, Miss.
Excessive heat warnings on Tuesday affected more than 17 million people and applied to almost all of Mississippi and wide areas of Alabama, Arkansas, northwestern Florida, Louisiana and western Tennessee. There was another excessive heat warning in less humid regions in the Southwest, and a heat advisory was in effect across much of Texas and Georgia.
“Heat exhaustion and heat stroke will be more likely if individuals and pets are not adequately cooled and hydrated,” read a bulletin from the National Weather Service in Jackson.
Linda Nolden, 60, a community services coordinator at the Tougaloo Community Center in Jackson, said in an interview on Tuesday that she could not remember a hotter day this year.
She was working to help dozens of older people at the center stay cool. “I guess with the energy bills being so high, a lot of the time they just come here to stay with me,” she said. “They can stay as long as they need to.”
People face a higher risk of heat stroke and heat exhaustion on days when the heat index is high — a measure not only of the temperature, but also of the amount of moisture in the air.
“When we get moisture in the atmosphere like we have today, it’s a lot harder for sweat to evaporate off of the body,” Mr. Winesett said.
“You definitely want to check on any elderly people or anyone you know who doesn’t have air-conditioning or don’t have a cool place to go,” he added. “If you’re working outside, take frequent breaks, drink a lot of water and stay hydrated.”
Ms. Nolden said she was encouraging everyone at the community center in Jackson to drink “water, water, water,” and stay out of the hot sun — including herself.
“I only went out there long enough to get my mail,” she said.
Cooler weather is expected to move into the region from the north on Wednesday.
While hot days are to be expected in the summer, climate scientists say heat waves are becoming more likely and hotter. The past five years have been the hottest on record, and the 10 hottest years have all occurred within the past two decades. Climate researchers have found that this past June and July were the warmest ever recorded.
Last month, another major heat wave spread across much of the United States, from the middle parts of the country to the Great Lakes and along the East Coast.