Postal worker dies in Dallas, woman found dead in Louisiana as temperatures reach record highs

A postal worker died on Tuesday while working his route in a Dallas neighborhood, according to the U.S. Postal Service, as Texas continues to experience record-high temperatures.

"The Postal Service is deeply saddened by the loss of life suffered yesterday involving a Lakewood Post Office Letter Carrier," the USPS told ABC News in a statement. "Our thoughts are with his family, friends and colleagues at this time."

USPS said it's implemented its Heat Illness Prevention Program for employees, and gives mandatory heat-related and safety training to all its employees.

"Our carriers deliver the mail throughout the year during varying temperatures and climatic conditions. This includes during the summer months when the temperatures rise throughout the country. The safety of our employees is a top priority, and the Postal Service has implemented a national Heat Illness Prevention Program (HIPP) for all employees," USPS said in a statement.

New Mexico, Texas, Oklahoma and Louisiana are under heat alerts Wednesday with the heat index -- what the temperature feels like with humidity -- expected to reach as high as 122 degrees in some areas.

1 heat-related death in Louisiana, health department says

The Louisiana Department of Health late Wednesday confirmed one storm-related death in Caddo Parish: a 62-year-old woman who was discovered in an area that did not have power for an extended period of time, officials said.

The cause of death was heat related, the state department of health said.

This comes as more than 500,000 customers are without power across the southern U.S., including 400,000 out in Texas, mostly from new outages, according to PowerOutage.us.

Record temps in Texas

Temperatures hit records on Tuesday and more are possible across Texas on Wednesday, including in Houston, where it could be up to 99 degrees; San Angelo, where it could be up to 110 degrees; Midland, where it could be up to 108 degrees; and Laredo, where it could be up to 113 degrees.

Temperatures in San Angelo and Del Rio, Texas, hit all-time record highs on Tuesday, reaching 114 degrees and 113 degrees, respectively.

The hottest place in the country Tuesday was Rio Grande Village, Texas, where temperatures reached 118 degrees. Record highs were reported all the way to North Dakota. Grand Forks hit 100 degrees, while Fargo reached 98 degrees and Jamestown hit 99.

Also, a new round of severe weather is expected Wednesday in the western Plains from South Dakota to western Texas, with the biggest threat being damaging winds and large hail.

Temperatures will cool slightly after Wednesday with thunderstorms rolling through, but temperatures are still expected to be above seasonal norms. Extreme heat will be back by next week.

Heavy rain in the Southeast

Six states from Florida to Virginia are under flood alerts for more heavy rain over the next 48 to 72 hours.

Some areas could see additional 5 to 7 inches of rain and more flooding is expected.

ABC News' Ahmad Hemingway contributed to this report.