Infants, toddlers and young children need outdoor activity to build strong bodies and minds, but they also require extra care in the heat. That shift makes questions about keeping babies safe more pressing, said Dr. Katherine Williamson, a pediatrician with Rady Children's Health in Orange, California. DON'T LEAVE KIDS IN THE CAREven in the shade and with open windows, car temperatures can rise dramatically in a short amount of time. If you return to a parked car with your baby on a hot day, ensure the metal parts of the car seat are also not too hot. To cool a hot car, experts recommend opening the windows for 10 to 20 seconds while running the air conditioning.