An awful milestone was reached this past weekend.

Eight hundred children have now died in hot cars since records began in 1998, according to  Golden Gate Weather Services, a private meteorology firm in California.

The 800th child to die was a  4-year-old boy in St. Paul, Minnesota, who was found dead on Saturday after he was left alone for hours in a hot SUV while his father was at work.

Horribly, dozens of small children who are alive now will be dead by the end of the summer, baked to death inside a hot car, if past years are any guide.

On average, 38 children die while trapped in hot vehicles every year, according to meteorologist Jan Null of Golden Gate Weather Services. Last year alone, a record 52 children died.

Null said that aside from crashes, heatstroke is the leading cause of death in vehicles for children 14 years old and younger.

How can this happen? Cars transform into ovens when direct sunlight heats objects inside. Temperatures can soar to 120 or 130 degrees even when the outdoor temperature is only in the 80s. The body's natural cooling methods, like sweating, begin to shut down once the core body temperature reaches 104 degrees. Death occurs at 107 degrees.

Children are particularly vulnerable because they have difficulty escaping a hot vehicle on their own, and their respiratory and circulatory systems can't handle heat as well as adults.

»RELATED: Georgia man to serve 10 years in prison for leaving twin toddlers in hot car

July is usually the deadliest month for children in overheated cars, with the highest toll of 16 deaths in 1999, Null said. "The warmer months are the biggest variable, but in summer months people's routines are changed, so that could be a contributor," Null said last year.

Since the mid-1990s, the number of children who have died from heat exhaustion inside vehicles has risen dramatically.

The requirement for children to sit in back seats after juvenile deaths from air bags peaked contributed to the climb since children are more easily forgotten in the back seat than the front.

Null said the circumstances of the deaths, from 1998 to 2018, are:

54.0% - Forgotten by caregiver              
26.3% - Gained access on their own              
18.9% - Knowingly left by caregiver               
0.9% - Unknown

Forgetting a child in the car can happen to anyone, Arizona State University psychologist Gene Brewer said last year.

"Often these stories involve a distracted parent," said Brewer. "Memory failures are remarkably powerful, and they happen to everyone. There is no difference between gender, class, personality, race or other traits. Functionally, there isn't much of a difference between forgetting your keys and forgetting your child in the car."

In Minnesota on Monday, the father of the dead child, 26-year-old Kristopher Taylor of Apple Valley, has been charged with second-degree manslaughter.

The temperature reached 70 degrees Fahrenheit, and the criminal complaint says the boy was in the sun.

Contributing: The Associated Press