 And within one hour, the inside of the vehicle got to be over 100 degrees. The heat poses a greater risk for children. Their bodies heat up three to five times faster than adults, according to the American Academy of Pediatrics. Dr. Thomas says parking in the shade or cracking a window is not enough. And although some newer vehicles have alerts to remind you to check the backseat, Dr. Thomas says oftentimes the tech does not directly sense for a rear passenger. So it's important not to rely on these systems.