Emergency Care For You

Heat Stroke and Hot Cars

By Gary Goodman MD, FACEP - Diplomate, American Board of Emergency Medicine; Attending Physician, Dept. of Emergency Medicine, Central Florida Regional Hospital; Assistant Professor of Clinical Medicine, UCF College of Medicine

“The thing about heat is, no matter how cold you are, no matter how much you need warmth, it always, eventually becomes too much.”   Victoria Aveyard, Glass Sword (Red Queen, #2).

Since 2017, the total number of children in the US that died from heatstroke after being left in a car is 72. Most of these children are under 3 years of age, according to www.noheatstroke.org.   

As an emergency physician practicing in Florida, I’ve seen the devastating impact of heat stroke countless times. The loss of these children’s lives is tragic but avoidable. 

Florida ranked second to Texas with 72 deaths recorded from 1998-2015. When adjusted for per capita (population per 1 million), Florida is the fifth worst state in the nation.[1]  

This mind staggering research comes directly from Mr. Jan Null, CCM, of the Department of Meteorology and Climate Science at San Jose University. “This danger exists despite public education, efforts, and lobbying for laws against leaving children unattended in vehicles,” Null said.[2]

Consider the human science: What is heatstroke? Heatstroke is defined as a condition by which the body develops hyperthermia (fever), during which the body experiences a failure of the thermoregulatory system.   

We manage heat exposure by way of the brain, circulatory system, and skin – in a way similar to a cooling system of a car.  Humans cool by ways of convection and evaporation of sweat.  Severe hyperthermia is defined as prolonged exposure to a body temperature of 104° F (40° C) or higher.  

During this syndrome, the body first develops thirst, dehydration, and perspires. As the temperature of the infant raises above 104° F, it can lead to the inability to perspire, confusion, mental agitation, and eventual coma. The body’s maximum temperature before protein starts to break down and organ failure ensues is approximately 106° F.  

Children and infants are more susceptible to heat illness due to their innate inability to regulate heat when compared to adults.[3]  The important point is that the danger is a function of not only the temperature, but time of exposure. 

The human body can only tolerate superheated environments for approximately 6-8 minutes before it loses its ability to respond. 

Now, let’s look at the car science:  Imagine a green house. No air movement. No internal cooling.  On days with temperatures as low as 70° F temperatures can reach 117° F in as little as 60 minutes with 80% of this being met with in the first 30 minutes![4] 

At 60 minutes, the internal vehicle temperature can raise to nearly 45° F above the outside.   Opening the window, even “cracking the windows” just 8 inches, had minimal effect on temperature rise and maximum temperature attained.[5]

Translation – it’s a myth! “Cracking the windows” will not only have little to no effect, but it is a practice that can and will lead to death as well.   

On July 29, 2016, Central Florida Regional Hospital and Seminole Safe Kids proved that internal car temperatures could be documented as high as 175° F with an outside temperature of only 94° F in one hour.  

In an attempt to demonstrate this, I sat in a car outside, with the windows closed, that reached a maximum of 140° F. I was only able to tolerate it for four minutes. Imagine a defenseless child, vulnerable adult, or pet.  

What can you do?  Life is a function of routines. We get up. We eat. We go to school or work. Parents if not home, have to arrange for day care. Transportation of the children to and from day care (or running an errand) is part of that routine. Add a simple stressor to that parent that day and that variance could lead to a change in that routine.  It is at that time, the biggest threat of forgetting a child can occur. 

It is important to recognize that vulnerable adults – senior citizens or developmentally delayed persons are also at risk.   This applies to animals left unattended as well.  Cars manufacturers are developing mechanisms within the car – i.e. weight sensors in the back seat that cause a dashboard indicator to ask, “did you bring your belongings,” for example.

Something as simple as putting your purse or shoe in the back seat could also trigger your memory to make sure you look back into the car, so this never happens again!

If you spot a person or a pet in a hot car, the laws detailing what you can do may vary by state. In Florida, laws have been recently changed to allow for good Samaritans to gain access to cars so long as the person immediately calls 911; uses force only necessary to gain access; and remains with the vehicle.  

With more public education and lobbying efforts, the needless loss of life can be prevented.

A version of this article originally appeared in Seminole magazine and EMpulse, a publication by the Florida College of Emergency Physicians (FCEP).


[3] Tsuzuki-Haykawak et al, Thermoregulation during heat exposure of young children compared to their mothers. Eur J Appl Physiol. 1995;72:12-17

[5] King et al, Heat stress in motor vehicles, a problem in infancy.  Pediatrics 1981; 68:579-582