As a long time hang glider pilot I have I have a particular fondness for those cumulus clouds and see them as a free ticket to air time.
Generally every cumulus cloud starts as a warm spot on the ground somewhere heated by the Sun. The warm ground heats the air around it and forms a bubble of warm air that can grow very large but eventually breaks loose from the ground and rises upwards pulling a column of more warm ground air along with it. This is called a thermal. That "thermal" of warm air continues to rise unseen until it hits the dew point where the moisture in the air turns to visible water droplets and forms cumulus clouds like the ones you see in those pictures.
Every cloud with a darker flat bottom effectively marks the top of a active thermal and a free elevator ride to cloud base, and when you see them lined up like in your picture below we call them "Cloud Streets". Cloud streets allows glider pilots to effortlessly soar from one cloud to the next for many miles like driving down a long "street" or highway.
So when I see clouds like that I always feel a sense of excitement and longing, like a kid driving past an amusement park, wishing I could be up there taking advantage of one of natures magical phenomenons.
