Why does the tire pressure decrease in rainy days?

When the tire temperature is low in rainy days or when the cold car starts, the air pressure will be lower. The following are the precautions for driving in rainy days: 1. Brake in advance in rainy days: the maximum braking distance of muddy roads can reach three times that of normal roads, and slow down in rainy days. 2. Don't reduce the tire pressure: reduce the tire pressure every rainy season in order to increase the contact area of the tire tread and prevent slipping. Increasing the contact area will reduce the pressure on the opposite side of the tire per unit area, thus weakening the force to remove the water film between the tire and the surface and making the tire more prone to skid. Therefore, reducing tire pressure can't prevent sideslip, but increasing tire pressure can prevent sideslip.