Air pressures decreases as one goes upwards. At 10 km height, the top of the troposphere, the pressure is less than one fifth of what it is at the surface. Remember most of the weather we get is due to things that happen in the troposphere.

Air pressure decreases as altitude increases (the higher up you go).Think a minute about being in a swimming pool ( one with a deep end of 12-15 feet). The deeper you dive down in the pool the more water there is above you and so the more pressure you feel. As you swim toward the surface the pressure decreases. The same is true for air. Although it is extremely light it does have a weight (which exerts pressure on you). At sea level all the weight of the atmosphere is on top of you. As you move to a higher altitude less and less air is above you and you therefore experience less air pressure.