And because warm water evaporates more readily than cold water, warmer sea surface temperatures contribute to more cloud formation and more rainfall downwind of the general flow of air currents. Soil moisture plays an important role in preventing or prolonging summer droughts. When the ground is wet, water evaporates as the day warms up. The warm, moist air rises until it encounters colder air high above the Earth's surface, leading to afternoon rainshowers. The water remains in the ground through the cool night, and the cycle repeats the next day.
Dry soil has the opposite effect on rainfall.
As the temperature rises during the day, the air near the Earth's surface heats up and rises, but does not contain enough moisture to form rainclouds. As each day passes more moisture is removed from the ground, enhancing the effect. Here's how the teleconnection works. The ITCZ in the Pacific helps determine the course of Pacific air masses flowing eastward toward North America. Thus, changing the ITCZ's position influences weather patterns all over the continent.