Why does the tire pressure decrease in rainy days?

When the tire temperature is low in rainy days or when the cold car is started, the air pressure will be lowered. The following are the precautions for driving in rainy days: 1. Braking in rainy days should be advanced: the maximum braking distance of the muddy road surface can reach three times that of the normal road surface, so slow down early in rainy days. 2. Don't reduce the tire pressure: reduce the tire pressure every rainy season in the hope of increasing the contact area of the tire tread to prevent skid. Increasing the contact area will reduce the pressure on the opposite side of the tire per unit area, which will weaken the force to remove the water film between the tire and the surface and make the tire more prone to skid. Therefore, reducing tire pressure can't prevent skidding, but increasing tire pressure can prevent skidding.