Summer is the time of storms in the deserts of much of the Southwest, just as it is the time of intense heat. Except for its mountainous areas, the Southwest receives most of its meager precipitation in this way. The weather systems that form the thunderstorms of summer are thus vital to the cycle of desert life, and were they ever to fail, so, too, would most of what lives in these dry regions.
When desert updrafts meet this moist Gulf air, they carry it skyward into cooler altitudes, where the moisture condenses into white, decorative cumulus clouds reminiscent of cauliflowers. If the air is sufficiently moist, the clouds can grow in height, becoming "towering cumulus" clouds. And if the updraft is strong, the air more saturated with moisture, and the differential in temperature between warm updraft and cool upper air sufficiently great, then you have all of the necessary elements to create a cumulonimbus cloud - also known as a potential thunderstorm.