8 Kids Die in Hot Cars So Far This Spring

That includes seven deaths in May alone, nearly double the typical number of heatstroke deaths during the month involving kids forgotten or neglected in vehicles, according to the advocacy group KidsAndCars.org. It provides a devastating reminder of the consequences of distraction and stress.

"It has everything to do with our brains letting us down at the worst possible moment," said Janette Fennell, president and founder of the group that works to raise awareness about the dangers of hot cars.

One child has died so far in June, a 2-year-old Escambia, Fla. boy, Hezekiah Brooks, who went missing Sunday on a 92-degree day and was found four hours later on the floorboards of his grandfather's car with the windows rolled up, police said.

Most deaths occurred when otherwise well-meaning parents or caregivers failed to notice that kids were still in the cars.

The May deaths occurred in four states over about two weeks, starting with the May 10 accident involving a 5-month-old girl who was left in a car at Riverside High School in El Paso, Texas. Her mother, Wakesha Ives, 37, is a teacher at the school, according to news reports. El Paso law enforcement officials told NBC News they're still investigating the case.

To date, 567 children have died after being left in cars in the U.S. since 1998, according to figures from the Department of Geosciences at San Francisco State University, which tracks reports.