The surge of heat is expected to push east into the central US, driving increased health risks, energy demand, and fire danger.
A 6-month-old boy died after he was left in a hot car for about seven hours, authorities said.
The daughter said she called in a nurse and bought two generators to get the air conditioning running, but that hasn't been enough to revive her 89-year-old mother.
Some 1.5 million CenterPoint Energy customers remained without power a day after the disaster. And while cooling centers are available, some households might not have to means to leave home.
When it comes to preventative measures and staying hydrated, Dr. Liz Weinandy said, "the best way to avoid dehydration is to drink before you get thirsty."
A prolonged heat wave is hitting the Midwest and Northeast this week in what could be the hottest stretch of weather for some people in 30 years.