Enlarge Mahaffey family photo William Dylen Mahaffey, age 4, died of hyperthermia June 13, 2010 inside his family's parked car, Frankin County, Alabama, authorities say. HEALTH REPORTER TWEETS HEALTH REPORTER TWEETS Nineteen children this year have died after overheating in hot cars, the most deaths in the first half of a year since researchers began tracking such deaths in 1998. Seven children died during the week of June 13, says Jan Null, an adjunct professor at San Francisco State University, who has recorded 464 heat-related deaths in children in the past 12 years. Thirty to 40 children die in hot cars every year, he says, and all of the deaths were preventable. TRAPPED: More kids dying in sweltering cars Eighteen percent of the children died after parents intentionally left them in a car, and 30% died after climbing into cars to play, says Null, who based his findings on news media reports. In the most recent case, a 2-year-old Phoenix child died Sunday after being left in a car for two hours. The temperature reached 108 degrees outside. The child's father found the girl after returning from running errands, The Arizona Republic reported. Null says parents should never leave children unattended in a car, because temperatures inside can rise quickly. Opening windows has almost no effect, because much of the heat radiates off seats and dashboards. Although rear-facing car seats have saved countless lives, their hoods can also cover babies completely, making them less visible to drivers. Slightly more than half of deaths occurred because parents forgot that children — many of them less than 1 year old — were asleep in the back, Null says. About half of those deaths occur when babies are with parents who don't usually drive them. Those parents appear to slip back into their usual routine, as if on "autopilot," says Lorrie Walker of Safe Kids USA, an advocacy group. "It's hard to imagine that you could lose track of a toddler," Walker says. "But apparently these people got in the car, drove to where they were going and forgot that they were supposed to stop at day care." Null says people can reduce the risks of these rare but catastrophic mistakes. All drivers should lock their cars to prevent kids from climbing inside and teach kids not to play in cars, he says. If you see a child alone in a hot car, call 911. Walker also suggests people place their purses or briefcases in the back seat, next to the car seat, to make sure they don't forget a sleeping child. Parents can call day care centers to make sure that their children arrive on time, or ask the center to call them if a child is more than a few minutes late, Null says. Also, carmakers could develop alarms that would sound if people fail to unbuckle a car seat harness after taking their keys out of the ignition, says Peter Pronovost, a leading safety researcher at Johns Hopkins University School of Medicine. Children are safest, he says, when people develop routines that make it difficult to put them in danger. "We should not focus on punishing the moms or saying 'Try harder,' " Pronovost says. "We need a system solution. Moms and dads will always be sleep-deprived and forgetful." Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more