do car trunks get hot

[VonSamuel]

Yes, car trunks can get extremely hot, often reaching temperatures that are dangerous for people, pets, and sensitive items. On a sunny day, the temperature inside a parked car's trunk can rapidly exceed 150°F (65°C), becoming significantly hotter than the outside air. This is due to the greenhouse effect, where solar radiation passes through the car's glass, is absorbed by interior surfaces like the trunk lid and carpet, and is re-radiated as heat, becoming trapped in the enclosed space.

The rate of heating depends on several key factors. The most significant is solar load—direct, intense sunlight causes temperatures to spike much faster than on a cloudy day or in a shaded spot. The car's exterior color also plays a major role; a black trunk lid absorbs more solar energy than a white or silver one, leading to higher internal temperatures. Finally, the duration the car is parked directly impacts the heat buildup. A car left for an hour will be hot, but one left for three hours in a parking lot can reach critical temperatures.

To illustrate how quickly conditions can change, consider the following temperature comparisons based on a 90°F (32°C) day:

Time Parked	Outside Air Temperature	Interior Cabin Temperature	Trunk Temperature
0 Minutes	90°F (32°C)	90°F (32°C)	90°F (32°C)
30 Minutes	90°F (32°C)	110°F (43°C)	120°F (49°C)
60 Minutes	91°F (33°C)	125°F (52°C)	140°F (60°C)
2+ Hours	92°F (33°C)	135°F (57°C)	150°F (65°C)+

This heat poses serious risks. It can permanently damage electronics, melt plastics like CDs or toys, and cause groceries like chocolate or soda to spoil. Most critically, it is never safe to leave a living creature in a parked trunk, even for "just a minute." Always park in the shade, use a sunshade for the rear window, and never use the trunk as a temporary holding space for anything heat-sensitive.

[AnastasiaLynn]

Absolutely, and it happens way faster than you'd think. I learned my lesson after leaving a case of water bottles in there one summer afternoon. When I opened the trunk an hour later, the plastic bottles were so hot I couldn't even hold them comfortably. It felt like an oven. Now, I never leave anything in there that can't take the heat, especially groceries. That quick stop at the store can turn your ice cream into soup.

[CoreyFitz]

Think of your trunk as a metal box sitting in the sun. It has no ventilation, so all the heat from the sun beating down on the car's exterior gets trapped inside. The dark-colored interior fabrics and plastics absorb that energy and radiate heat, causing the temperature to soar. This is why a simple errand can result in a trunk that's dangerously hot to the touch. The key takeaway is that it's an enclosed space with no way for heat to escape.

[StGenevieve]

On a long road trip, I'm always careful about what goes in the trunk. While the cabin has air conditioning, the trunk does not. Luggage is fine, but I have a strict rule: no electronics, no medications, and definitely no snacks. I once made the mistake of putting a bag of chips back there, and when I opened it at our destination, several bags had popped open from the pressure and heat. It's a separate, unregulated environment that you have to think about independently from the rest of the car.

[NathanRose]

From an engineering perspective, the trunk is a prime example of thermal energy transfer. Solar radiation is the primary heat source. Materials with low albedo, like a black painted surface, absorb a high percentage of this radiation. With minimal conductive cooling to the outside air and no convective airflow, the internal temperature climbs until an equilibrium is reached, often at a dangerously high level. This is a fundamental design characteristic of an enclosed vehicle compartment, not a flaw.