As an air parcel rises, it expands and cools. If the air is dry, it cools at the Dry Adiabatic Lapse Rate. However, once the air cools to its dew point, water vapor condenses into clouds. This phase change is an exothermic process, releasing latent heat into the air parcel. This added heat offsets some of the cooling caused by expansion. Therefore, moist air stays warmer than dry air at the same altitude, which is a major factor in atmospheric stability and the development of massive, towering thunderstorms that can reach the tropopause.