How much of an influence does pressure have on phase changes? It has a major influence. This influence is easily seen in cooking. If you were cooking while located at a high-altitude, the boiling point of water is actually lower at higher altitude due to a decrease in atmospheric pressure. Not only does this cause longer cooking times but it also causes an alteration of recipe ingredients. To experience this effect, you would need to be at an elevation above two thousand feet. At this altitude, water boils at approximately 98°C.