What causes car windows to fog up in the rain?

[GavinFitz]

The reason car windows fog up in the rain is due to high air humidity and significant temperature differences between the inside and outside of the glass, causing water vapor to condense on the glass. The solutions are: 1. Use the air conditioning defogging function by turning on the front window defogging mode, increasing the fan speed, and lowering the temperature; 2. Activate the one-touch defogging function; 3. Increase air convection by opening windows to reduce the temperature difference inside and outside the car, thereby weakening the conditions for fog formation; 4. In winter, use the air conditioning's hot air defogging function. Do not turn on the air conditioning immediately after starting the car. Wait a few minutes for the engine to warm up and the water temperature to rise, then start heating, increase the fan speed, and turn on the front window defogging mode; 5. Spray defogging agent evenly on the glass surface and wipe it clean with a dry towel; 6. Make a homemade defogging solution by mixing dish soap and water in a 1:6 ratio in a bottle. Spray and wipe before driving; the effect is similar to commercial defogging agents, though the duration is slightly shorter.