Four young children were allegedly left inside a locked car in Sydney's west on Wednesday afternoon, as the mercury hit its peak of 40.9 degrees.
Police and paramedics were called to the Officeworks car park on Canterbury Road at Bankstown at 3pm, after being alerted by a concerned passerby.
The children, aged 9, 8, 7 and 6, were crying inside the car at the time, the passerby said.
The children were helped from the vehicle by witnesses and were not injured.
Police said the driver, a 44-year-old woman, had left the scene, but later assisted police at Bankstown police station.
She was charged with leaving a child or young person in a motor vehicle causing emotional distress.
Temperatures soared in Sydney on Wednesday during the first heatwave of 2017, with the mercury reaching 42 degrees in western Sydney and 38 degrees in the city in the afternoon.
Wednesday was the fifth day of this summer that temperatures exceeded 35 degrees, the most since 1991-1992.
Police warn that, on a typical summer day, the temperature inside a car can reach 50 to 60 degrees, even with the windows rolled down.
The woman is due to appear in Bankstown Local Court on February 22.