A baby girl has died and another is being treated in hospital after they were left trapped in cars in suburban Indianapolis during near-record heatwave.
A four-month-old was trapped in her car seat for what police say was an "extended period of time" in the middle of the afternoon, according to Fox News.
She was rushed to the hospital on Saturday by a family member where she was confirmed dead.
Her father, 19-year-old Joshua Strycinski, was arrested and preliminarily charged with neglect of a dependent resulting in death.
In a separate incident, police broke a side window of a Ford Explorer SUV to rescue a 16-month-old girl who was locked inside.
Officers were called to parking lot of a store called Simply Chic and found the child, police spokesman Tom Weger said.
The temperature inside the vehicle was 124 degrees.
The girl began having seizures shortly after being taken into an air-conditioned building and she is now being treated in Peyton Manning Children's Hospital in Indianapolis.
Weger said the girl's mother, 30-year-old Meg Trueblood, has been charged with neglect.
Trueblood allegedly told police she had left the child inside the car for an hour while she went shopping.
Temperatures have been soaring in more than 20 states as a heatwave swept across the US.
It was 40.5C (105F) in Louisville, Kentucky, 38.5C (101F) in Philadelphia, and 35C (95F) in New York.
A record of 40C (104F) was set in Sioux Falls, South Dakota, and Baltimore set a record at 39C (102F).
At least 30 people have died in the heat, including nine in Maryland and 10 in Chicago, mostly among the elderly.
Officials said the heat caused highways to buckle in Illinois and Wisconsin, and in Maryland, investigators said it is likely that heat caused rails to kink, forcing a train to partially derail on Friday afternoon.
No one was injured and 55 passengers were safely evacuated.
"This is becoming a black swan of heatwaves, in the sense that it's such a long heatwave, such a severe heatwave and encompassing such a large area," said Chris Vaccaro, spokesman for the National Oceanic and Atmospheric Administration.