What is the Temperature Inside a Car Trunk at 40 Degrees Celsius in Summer?

[McTeagan]

In summer, the temperature inside a car trunk at 40 degrees Celsius can reach around 50 degrees Celsius. Below are some extended solutions for dealing with excessively high temperatures inside a car during summer: 1. Park the car with its rear facing the sun: Choose a shaded parking spot if possible. If you have no choice but to park under direct sunlight, position the car so that the rear faces the sun. The rear window is smaller, allowing less sunlight to penetrate and reducing heat buildup in the cabin compared to parking with the front facing the sun. It's best to use a car cover or a sunshade on the windshield to block direct sunlight. 2. Spray water to cool down: When the interior temperature is high, you can spray some water inside the car. Adding a bit of alcohol to the water helps it evaporate and absorb heat faster. Open the doors, spray a few times inside, then close the doors without opening the windows. The temperature will drop in a few minutes. Note that 100% pure alcohol has a flashpoint of 75°C, and the flashpoint increases as the concentration decreases. It's recommended to use 75% medical-grade alcohol diluted with water at a ratio of 1:10.

[McMatthew]

Every time I drive in the scorching summer heat of 40 degrees Celsius, I find the trunk temperature truly alarming—it’s like a small oven. This is because the trunk is an enclosed space with poor ventilation, allowing heat to accumulate rapidly. When the outside temperature is 40 degrees, the trunk temperature can soar to over 60 degrees or even higher, making it hotter than the engine bay. I once tested it by placing a thermometer inside, and within just 20 minutes, it showed 65 degrees. It’s not just uncomfortably hot—it can also damage items: electronics may overheat and explode, food can spoil quickly, or plastic items may warp. What’s even more concerning is that it harms the car itself, such as accelerating the aging of trunk seals and increasing the risk of rust on metal components. My advice is to avoid leaving valuables in the trunk for long in hot weather, or use sunshades for insulation. Whenever possible, park in the shade to keep the trunk temperature lower.

[LaRicardo]

As someone who drives frequently, the temperature issue in the trunk during summer really bothers me. On a 40-degree day, the trunk feels like a steamer. I've measured it several times, and the temperature easily exceeds 60 degrees, over 20 degrees higher than outside. Why is it so hot? The trunk has no windows for ventilation, so the heat gets trapped inside after being exposed to the sun. Once, I forgot to take out my pet's toys, and they ended up melting and deforming, which really startled me. It doesn't just affect the safety of items but also poses health risks, like spoiled medicine or food causing poisoning if consumed by mistake. I think simple precautions can help: open the trunk for a while to let it breathe when parking, or use reflective materials on the inner walls to dissipate heat. It's best to develop a habit of quickly unloading groceries and not letting the trunk become a hot pot.

[CourtneyDella]

From a scientific perspective, the temperature inside a car trunk in summer when it's 40 degrees Celsius outside is extremely dangerous. With an ambient temperature of 40°C, the trunk can heat up to over 65°C because the heat has nowhere to escape. This can easily cause damage to items, such as battery swelling or food spoilage. It's recommended to measure with a thermometer or simply use your sense of touch: if the trunk feels hot to the touch when opened, that's a clear sign. Pay more attention to this to avoid losses.