* Moisture: These clouds are typically cumulonimbus clouds, also known as thunderheads. They form when warm, moist air rises rapidly, cooling and condensing into water droplets or ice crystals.

* Vertical Development: Cumulonimbus clouds are characterized by their towering, vertical development. This vertical growth allows them to carry significant amounts of moisture high into the atmosphere.

* Instability: The rapid ascent of air within these clouds creates a powerful updraft that can lead to instability, with conditions conducive to thunderstorms.

* Precipitation: The condensation of moisture within these clouds often results in heavy rainfall, sometimes accompanied by hail, lightning, and strong winds.

Therefore, when you see dark black clouds in the sky, it's a good idea to take cover and seek shelter as a storm may be approaching.