Why is there a layer of frost on the outside of the car in summer and why does it feel cold?
4 Answers
In summer, a layer of frost forms on the outside of the car because the external temperature and humidity are high, while the interior temperature is low, causing moisture in the air to condense on the exterior glass. Methods to defog car windows in summer: Warm Air Defrosting Method: Wait for the engine coolant temperature to rise, then turn on the warm air function and direct it toward the windshield. Once the frost melts, you can use the windshield wipers to speed up the removal. Windshield Washer Fluid Defrosting Method: Choose a windshield washer fluid with a freezing point of -30 degrees Celsius. Evenly spray the fluid on the windshield, wait a moment for the ice to melt, and then wipe it clean with a car cloth. You can also use a spray bottle for easier application.
I've also experienced parking my car outside in the summer, only to find the roof feeling frosty and cool the next morning. This actually happens because nighttime temperatures drop rapidly, especially when humidity is high. The metal or glass surfaces of the car cool faster than the surrounding air, causing moisture in the air to condense into tiny water droplets that resemble frost. This phenomenon is more common in hotter and more humid regions. I recommend choosing sunny parking spots whenever possible to minimize shade coverage. Regularly waxing your car can also make the surface smoother, preventing dew from accumulating and making it feel less damp and cold. If parked on a slope or in a poorly ventilated area, this effect becomes more pronounced. In short, don't worry—it's not a malfunction, just pay attention to maintaining your car's paint finish.
Why does the car surface feel like it's covered in frost and cool in summer? I've researched this, and it's mostly caused by dew condensation. After a hot day, when temperatures drop sharply at night, the car cools down quickly. Moisture in the air then condenses into water droplets upon contact with the cold surface. If the air conditioning is on while driving, the exterior near the vents becomes particularly cold, making it easier for moisture in the warm air to condense into a thin frost layer. From my checks, cleaning the car paint and windows can reduce residue that attracts moisture. Keeping the AC condensation pipes clear also prevents unusual external condensation. Simply wiping it dry with a towel will do—it's not a major issue but can affect comfort.
As an ordinary car owner, I often notice a cool, frost-like layer on the roof of my car on humid summer mornings. The reason is simple: the temperature drops at night, causing moisture to condense on the car's surface, forming dew. This is especially noticeable when humidity is high or after rain, and it feels damp and cold to the touch. My solution is to gently wipe it off with a sponge before driving or park the car in a spot with direct sunlight. If the air conditioning is turned up too high, the temperature difference between the inside and outside of the car can worsen condensation, so I reduce the fan speed or close the windows. Additionally, avoiding parking in the shade immediately after washing the car can help minimize this phenomenon. In short, there's no need to rush—just let the natural wind blow for a while, and it will disappear on its own.
