It is a rule that as we go up,the air pressure decreases.And as we know,in high temperature the air is in low pressure .But as we go up the air becomes cold not hot.So whyvis that,as we go up the air pressure decreases.

Due to increase in the altitude of the atmosphere , atmospheric pressure decreases as we go higher up above the earth's surface.Atmospheric pressure is the pressure applied at a point due to the weight of the air above that point. As we go up, the altitude increases and the amount and the density of air above it decreases. So the pressure due to it decreases
Higher region is cold due to Cold Advection A
: cold air moves into a warmer region. Cold advection is the process in which the wind blows from a region of cold air to a region of warmer air. As the cold advection persists, temperatures in the warmer region will begin to decrease as the colder air moves into the region of warmer air.