A hot car can potentially kill bed bugs, but simply parking an infested vehicle in the sun doesn’t guarantee that every bed bug and egg inside will die. A closed car in direct sunlight can reach temperatures that are lethal to bed bugs on exposed surfaces, while seams, cushions, luggage and other insulated hiding places may remain considerably cooler.
The EPA actually includes a hot, closed car in the sun among possible DIY heat approaches for suitable bagged belongings, although it warns that success depends on climate and other conditions. That distinction is important. Using the controlled heat inside a sunny vehicle to treat small contained items is different from assuming sunlight has treated the entire vehicle.
How Much Heat Does It Take to Kill Bed Bugs?
Bed bug mortality depends on both temperature and exposure time. Higher temperatures kill them faster, while lower temperatures have to be maintained longer.
In controlled laboratory experiments, researchers measured an LTemp99 of 48.3°C (118.9°F) for adults and 54.8°C (130.6°F) for eggs. These figures represent temperatures associated with 99% mortality under the experimental conditions rather than universal temperatures at which every bed bug immediately dies.
Time becomes especially important at lower temperatures. At 45°C (113°F), the same research found an estimated LTime99 of 94.8 minutes for adults, while eggs survived considerably longer. At 48°C (118.4°F), eggs survived for about 71.5 minutes. The broader relationship between heat and bed bug mortality therefore can’t be reduced to reaching one temperature for a moment. The insect itself has to experience sufficient heat for sufficient time.
How Hot Does a Car Get in the Sun?
A closed vehicle can become much hotter than the surrounding outdoor air.
Researchers from Arizona State University and the University of California San Diego measured cabin and surface temperatures in vehicles parked in direct sunlight and shade during hot summer conditions. After one hour in the sun, the average cabin temperature reached 116°F, while seats averaged 123°F, steering wheels 127°F and dashboards 157°F. Vehicles parked in the shade were substantially cooler, with cabin temperatures around 100°F and seats averaging 105°F after the same period.
Those measurements demonstrate that some surfaces inside a sun-exposed car can enter a temperature range capable of killing bed bugs. They don’t demonstrate that a bed bug on a seat received a full hour of exposure at 123°F, however. The seat warmed progressively during that hour and reached the reported temperature at the end of the measurement period.
For the same reason, the 123°F seat measurement can’t simply be placed beside the laboratory’s 118.9°F adult LTemp99 and treated as proof that one hour in the car would kill 99% of adults. The temperature history experienced by the insect is different.
The Hiding Place Matters More Than the Hottest Surface
A dashboard reaching 157°F doesn’t tell us what is happening several centimetres inside a seat cushion.
Bed bugs tend to hide in protected spaces, including seams, folds, upholstery joints and narrow gaps. Heat has to penetrate those locations before it can kill the insects inside. A surface can therefore become lethally hot while a protected harborage remains cool enough for survival.
A bed bug heat experiment involving mattresses demonstrates how extreme that difference can become. Researchers wrapped mattresses in black plastic and exposed them to summer sunlight for more than nine hours. The sun-exposed surfaces reached as high as 85°C (185°F), yet portions of the mattresses remained around 35 to 36.5°C (95 to 97.7°F). The researchers concluded that this solar method didn’t provide reliable thermal control.
A car seat isn’t the same as a mattress, but the experiment demonstrates the underlying problem clearly: an extremely hot exposed surface doesn’t prove that lethal heat reached every protected location inside an upholstered object.
Can You Kill Bed Bugs in Belongings Inside a Hot Car?
This is where a hot car has a more defensible practical use.
The EPA specifically says black plastic bags can be placed in a hot, closed car in the sun as a possible nonchemical method for suitable belongings. It also cautions that success depends on climate and other factors and that DIY heat treatments may fail.
Containment makes this approach more practical because you’re trying to heat a defined group of items rather than an entire vehicle with numerous insulated hiding places. Even then, the temperature that matters is the temperature reached where the bed bugs are located, not the dashboard temperature or the outdoor weather reading.
An older EPA recommendation similarly noted that black plastic bags in sunlight may work when their contents become sufficiently hot. Using a thermometer to monitor the coolest relevant part of the treated contents provides much more useful information than assuming a black bag or closed vehicle became hot enough.
Heat-sensitive belongings also shouldn’t automatically be placed inside a very hot vehicle. Electronics, medications, pressurized containers, batteries, plastics and other materials can be damaged or become hazardous at elevated temperatures.
Does Parking the Entire Car in the Sun Treat an Infestation?
It shouldn’t be relied upon as a complete vehicle treatment.
Sunlight can produce lethal temperatures in parts of a car, particularly exposed dashboards, seats and other surfaces. However, a bed bug could be sheltered inside upholstery, beneath a seat, under carpeting, behind interior trim or in another location that heats much more slowly.
Weather introduces another layer of uncertainty. Outdoor temperature, cloud cover, time of day, vehicle design, orientation, shade and duration of exposure all affect interior temperatures. The hot-car research also found that different vehicle types heated at different rates.
The EPA’s recognition of a hot car therefore shouldn’t be interpreted as a recommendation to park an infested vehicle in the sun and declare it bed bug free. Its guidance specifically discusses using the environment to heat-treat belongings, while warning that DIY heat treatment can fail.
Does Parking in the Shade Kill Bed Bugs?
The available vehicle-temperature measurements make shade considerably less promising.
After one hour, shaded vehicles in the Arizona study averaged about 100°F inside, with seats around 105°F. Those temperatures shouldn’t be considered adequate bed bug heat treatment based on established thermal-control research.
More importantly, even the temperature of the cabin air isn’t necessarily the temperature reached inside protected harborages. If you’re trying to determine whether a heat treatment succeeded, measuring only the surrounding air can give a misleading impression of what the insects actually experienced.
What Should You Do If You Find Bed Bugs in Your Car?
Start by inspecting the areas where bed bugs could hide and physically removing bugs where possible. Vacuuming accessible seat seams, carpeting, floor mats and crevices can reduce the number present, although vacuuming alone won’t guarantee elimination.
The EPA recommends thorough vacuuming as part of bed bug control and says the vacuum contents should be sealed and discarded outside after use. Removable clothing, blankets and other dryer-safe fabrics can instead be treated with a household dryer on high heat for 30 minutes, which the EPA says kills bed bugs and eggs.
The complete approach to getting rid of bed bugs in a car should therefore focus on inspection, physical removal and controlled treatment of removable belongings rather than relying on whatever temperature the vehicle happens to reach in the sun.
Questions About Hot Cars and Bed Bugs
Will leaving a car in the sun for one hour kill bed bugs?
Not reliably. Research shows that some vehicle surfaces can reach bed bug-lethal temperature ranges within an hour under hot, sunny conditions, but that doesn’t mean every bed bug experienced that temperature for the entire hour. Protected hiding places may also remain much cooler.
Will leaving a car in the sun all day kill every bed bug?
It may expose some bed bugs to lethal heat, but there isn’t enough evidence to guarantee complete elimination throughout a vehicle. Temperature needs to be lethal in the coolest harborages, not merely on exposed seats or the dashboard.
Can black plastic bags help inside a hot car?
Yes, this is one situation specifically recognized by the EPA. Suitable belongings can be sealed in black plastic bags and placed in a hot, closed car in direct sunlight, although the EPA cautions that success depends on climate and other factors. The contents themselves must become sufficiently hot.
Does cracking the windows help?
No reason exists to crack the windows when the goal is retaining heat. The vehicle-temperature research showing very high interior temperatures involved closed vehicles, and increasing ventilation would work against heat accumulation.
Can you tell whether the treatment worked from the dashboard temperature?
No. The hottest surface isn’t the important measurement. Heat treatment succeeds only if lethal temperatures reach the bed bugs themselves, including those inside seams, folds and other protected locations.