(CNN) - (07/30/19) - Vehicular heatstroke, the devastating effects of a child being left in a hot car: It's every parent's unfathomable nightmare, yet it happens several times a year.
Since 1998, 818 children have died from pediatric vehicular heatstroke, which occurs when a child's body temperature rises to 104 degrees. A temperature of 107 degrees is lethal, according to the National Highway Transportation Safety Administration.
The tragedy can happen almost anywhere, and while hotter months are the riskiest, the circumstances surrounding child vehicular heatstroke are varied.
Hot car deaths are a consistent problem
Heatstroke kills 38 children every year on average, according to the National Safety Council. These include instances in which a child has been forgotten in a car, when they accidentally lock themselves in a car or trunk or, in a small number of cases, when a child has been intentionally left in a car.
NoHeatStroke.org, a data site run by San Jose University's Department of Meteorology & Climate Science, has been collecting data on these incidents since 1998. 2015 had the lowest rate of incidents, with 24.
So far, 23 children have died from being left in a hot car in 2019.
On Friday, 1-year-old twins in New York died after their father left them in a car for eight hours while he went to work, police say. Both children's body temperatures reached 108 degrees, according to the Office of the Chief Medical Examiner.
A 2-year-old boy was found dead in a day-care center's van in Oakland, Florida, on Monday. Temperatures outside peaked around the low 90s, so it's possible that heat caused his death, police said.
If confirmed, his death would mark the 24th hot car death this year.
2018 saw more hot car deaths than any other year
2018 was the deadliest year for child vehicular heatstroke in 20 years, with 52 children between 7 weeks and 5 years old dying after being left in cars.
Jan Null, meteorologist and founder of NoHeatStroke.org, said that not even temperature can explain the uptick in deaths. The fewest hot car deaths occurred in 2015, which coincidentally saw the highest average temperature at the time of death in five years, at 92.2 degrees.
It's impossible to predict when hot car deaths will occur, but the 2019 count is lower than at this point in 2018. There are 11 fewer deaths now than there were on this date last year, when there had been 34 deaths, he said.
It can happen anywhere
It seems obvious that states with the highest temperatures are usually where the most deaths by vehicular heatstroke happen, but there have been instances recorded in nearly every state.
Texas and Florida lead the United States in heatstroke deaths, with 123 and 91 respectively between 1998 and 2018, according to NoHeatStroke.org.
Per capita, Arkansas leads the country in hot car deaths, with 29.1 per 1,000 people over the 20-year period.
Summer always brings an onslaught of deaths
Between 1998 and 2018, 189 children have died of heatstroke in July, more than any other month, NoHeatStroke.org reported.
Temperatures inside a car can climb 20 degrees in just 10 minutes, according to the National Highway Transportation Safety Administration, and often, that's enough to cause hyperthermia. Within an hour, car temperatures can rise more than 40 degrees, even when temperatures are low.
Though hot car deaths occur more frequently in the summer, they can occur even when the weather is cool. A 2005 study found that even when it's 72 degrees outside, the temperature inside a car parked in the sun climbed to 117 degrees in 60 minutes.
Rolling the window down doesn't make a difference, either. The study showed that the parked car ended up at the same temperature after an hour in the sun, whether or not the window was open.
Most hot car deaths are accidents
The majority of heatstroke deaths occur by accident, according to NoHeatStroke.org.
More than half happen when parents forget about their child in the backseat. Another 26% of children after entering the car on their own, and about 18% were left there intentionally.
A 2019 study found that more than 60% of the adults held responsible were parents of the victim. Just 7% were paid child-care providers, though they were 53% more likely than parents to be sentenced to less than five years in prison.
About 87% of heatstroke victims are 3 or younger, according to NoHeatStroke.org. Nearly one-third of deaths occur in infants under 1 year old.
Some states have outlawed leaving kids in cars alone
As of July, 21 states have enacted laws that make it a crime to leave a child alone in the car in the first place, regardless of the outcome, NoHeatStroke.org reported.
Four states allow a brief period of time that a child can spend alone in a car before it becomes illegal. Texas and Hawaii allow a five-minute maximum, Illinois allows 10 minutes, and Florida allows 15 minutes.
Additionally, 21 states have Good Samaritan laws that allow citizens to "rescue" a child alone in a car if they perceive the child to be in danger, even if they break through a window. Many, but not all, of states with those laws have outlawed leaving a child in a car unattended.
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