These pretty cotton-ball clouds arrived on the horizon while I was enjoying some deck time. Although they look harmless, cumulonimbus clouds can pack a very serious wallop, especially if they get together in a group or start growing vertically. These clouds are doing both, and a bit later we had an enormous thunder storm.
Because cumulonimbus clouds are formed by rising water vapour droplets, powerful upward air currents can develop and possibly lead to unstable and turbulent air that could become seriously problematic for aircraft. In their most severe forms, cumulonimbus clouds can lead to massive thunder storms or tornadoes.
So when your flight is delayed because of summer weather, just remember that although these clouds look like harmless powder puffs, you probably wouldn’t want to fly through one.