Heat vs. Cold: Which Is More Dangerous for Kids in Cars?

Not long ago, a friend’s simple query on Facebook triggered my own curiosity: why don’t we hear about children dying after being left in a vehicle on a very cold day? It’s a pertinent question, given the tragic consequences when small children (or pets) are inadvertently left in the car on a sunny, warm day. When it comes to the environment inside a closed vehicle, it appears that warm weather is indeed far riskier than cold weather, for a variety of reasons.

Jan Null (Department of Meteorology and Climate Science, San Jose State University) has tracked close to 700 deaths of children left in cars since 1998. However, he knows of only a couple of cases where children died from being in a cold vehicle. Null suggested I check with Dr. Leticia Ryan, an assistant professor of pediatrics at Johns Hopkins Children’s Center. Ryan agreed that the question was a good one: “Children are at increased risk for both hyperthermia [elevated body temperature] and hypothermia [reduced body temperature] in comparison to adults.” However, like Null, Ryan wasn’t aware of any research focused on the different responses to heat vs. cold in vehicle interiors.

To explore the question further, I held an email brainstorm with Rebecca Morss and Julie Demuth, both of whom study the intersections of weather, warnings, and society at the National Center for Atmospheric Research. Morss and Demuth pointed out several factors that would presumably lead to a greater risk to children and pets left in cars during warmer times of the year. 

—Sunshine can only warm a vehicle, regardless of the temperature outside. This is why it doesn’t have to be a scorching-hot day to produce deadly heat inside a closed car (see Figure 1). On a bright, cold winter day, the same effect could help keep a vehicle’s interior less chilly than it would otherwise get.


Figure 1. Even when temperatures outside are only 80°F, sunshine entering a closed vehicle can push the temperature to 109°F in just twenty minutes. After an hour, the car’s interior air can reach a blistering 123°F. Cracking windows does not reduce the ability of the air to reach such high temperatures. The sunshine entering the car rapidly heats up surfaces (the dashboard or steering wheel can reach 180 – 200°F on an 80°F day). These surfaces, in turn, heat up the interior through convection and conduction as well as by longwave radiation, in much the same way that an asphalt parking lot sends heat upward. An hour’s worth of warming is depicted in this QuickTime animation. Image credit: GM and Jan Null.


—Being in a closed vehicle minimizes the effect of wind chill, which could otherwise exacerbate the bodily heat loss for a given air temperature.

—Unless a cold front is moving in, the outdoor temperature will typically rise during the course of a winter day, thus reducing the potential temperature drop within a vehicle.

—Morss speculates: “I can imagine why one is less likely to leave a child in a car on a cold day, because you'd be more likely to go back into your car to grab something (coat, mittens), or you'd have a cue when you got out of the car and felt the bitter cold that would make you think ‘did I give my child warm enough clothes today?’ and thus think about your child.”

A few stats and safety tips
Last year (2015) saw 24 vehicular heat stroke deaths, the least for any year since Null began compiling data in 1998. However, 2016 is off to a bad start, according to Null, with 16 deaths already recorded as of June 30. Null’s website noheatstroke.org includes a set of frequently updated statistics that bring home the problem vividly. Of the 661 such deaths recorded from 1998 through 2015, just over half involved children who were “forgotten,” many of them left in a vehicle by a parent or caregiver rushing to work in the morning. Latitude is not a guaranteed defense, as 2016 has already seen confirmed deaths as far north as Iowa and New York.

Here are Null’s safety recommendations:

—Never leave a child unattended in a vehicle—not even for a minute!
—If you see a child unattended in a hot vehicle, call 911.
—Be sure that all occupants leave the vehicle when unloading. Don't overlook sleeping babies.
—Always lock your car and ensure children do not have access to keys or remote entry devices. Teach children that vehicles are never to be used as a play area.
—If a child is missing, always check the pool first, and then the car, including the trunk.
—Keep a stuffed animal in the carseat, and when the child is put in the seat, place the animal in the front with the driver. Or place your purse, briefcase, or cell phone in the back seat as a reminder that you have your child in the car.
—Make "look before you leave" a routine whenever you get out of the car.
—Have a plan that your childcare provider will call you if your child does not show up for school.


Don’t forget your furry companion!
Hundreds of pets are believed to die around the country after being left in hot cars. The Humane Society offers these tips on how you can help if you see a pet in a parked car on a sunny summer day:

—Take down the car's make, model and license-plate number.
—If there are businesses nearby, notify their managers or security guards and ask them to make an announcement to find the car's owner.
—If the owner can't be found, call the non-emergency number of the local police or animal control and wait by the car for them to arrive.

The American Veterinary Medicine Association suggests: “Before you put your pet in the vehicle, ask yourself if you really need to take your pet with you--and if the answer is no, leave your pet safely at home.”

Several states now have Good Samaritan hot-car laws that allow private citizens, in some circumstances, to break into motor vehicles if they notice a child or an animal is in jeopardy. Various types of hot-car laws are now on the books in 21 states, and bills are now pending in California and Michigan. The Animal Legal Defense Fund has compiled a useful state-by-state overview of the protections now in force and those being considered.

Eastern North Pacific is primed for tropical development next week
Long-range forecasts from the ECMWF and GFS models continue to flag the possibility of one or more tropical cyclones developing next week over the eastern North Pacific. This region will be under the influence of a strong convectively coupled Kelvin wave (CCKW) as well as an active Madden-Julian Oscillation (MJO), both of which will favor rising motion and tropical development in the eastern Pacific over the first few days of July. (See our Wednesday post for more background on CCKW and MJO activity.) Wind shear is weak to moderate across the region, and sea surface temperatures are 0.5°C to 2°C above average throughout the area north of about 8°N, despite the presence of cooler-than-average waters closer to the equator associated with the trend toward La Niña.


Figure 2. Infrared GOES-East satellite image for the eastern North Pacific, valid at 1515Z (11:15 AM EDT) Friday, July 1, 2016. The disturbed weather stretching from west to east is associated with an active monsoon trough. Image credit: NASA Earth Science Office.

The first in our potential series of East Pacific tropical cyclones is likely to be Invest 94E, now located well south of Acapulco, Mexico. In its 10 AM EDT Friday tropical weather outlook, the National Hurricane Center gave 94E a 30 percent chance of development by Sunday and an 80 percent chance by Wednesday. Another disturbance located further west has only a limited amount of convection (showers and thunderstorms) with it, but NHC gives it a 20 percent chance of development over the next five days. Several other weak centers of low pressure extend east along the monsoon trough that includes both of these systems (see Figure 2), yet it remains unclear which one(s) will have the best chance of development. NHC summed it up nicely in its 10 AM EDT Friday tropical weather discussion for the eastern Pacific: “Model guidance is consistently showing further development of one or more of these low pressure areas, but continues to be inconsistent regarding the details such as when, where and to what extent.” Whatever does develop over the next few days across the region will likely track well offshore and pose little or no threat to land.

Meanwhile, in the U.S., there are no large areas of significant severe weather anticipated for the holiday weekend. Very heavy rains (locally 4” to 6”) and a few severe storms are expected as a weak upper impulse traverses a frontal zone from Kansas to southern Illinois and Indiana, moving into the central Appalachians by Monday and Tuesday. Residents of West Virginia hard-hit by flooding last week will need to monitor this threat.

Jeff Masters will be back on deck next week. In the meantime, have a great weekend, everyone. If you’re in the U.S., Happy Fourth of July--and if you're a Canadian, Happy Canada Day!

Bob Henson


Figure 3. Central surface pressures in potential tropical cyclones depicted by members of the GEFS ensemble run from 06Z Friday, July 1, 2016, valid at 06Z Thursday, July 7. Each central pressure is in millibars, with the preceding “9” or “10” lopped off. Colors indicate the normalized spread, or how much the central pressures deviate from typical surface pressure. The predicted centers toward the west are associated with Invest 94E. Image credit: tropicaltidbits.com


Figure 4. Members of the GEFS ensemble run from 06Z Friday, July 1, 2016, show a variety of potential tracks for Invest 94E, all of which would take the system well away from the Mexican coastline.