On still, settled days when there is not enough moisture for them to grow into much bigger cumulus clouds, and there is not enough wind to scatter them, cumuli of fair weather hang around the sky in sparse flocks, like big sky sheep grazing in the low sky. Big for sheep that is; small in cloud terms, because the weather just doesn't have the energy to make them grow much bigger.

Cumuli of fair weather are the little ones of the cumulus family; they resemble less turbulent versions of the early stages of bigger cumuli, like the cumulus congestus or the towering stormclouds of the cumulonimbus. They are less tall and less busy, and they don't grow like other cumuli do. When the sky is populated with clouds like that, expect the weather to be fine for while yet.

Oolong recommends: http://www.cloudman.com/gallery1_1.html