A tall cumulus cloud is typically associated with thunderstorms and unstable weather conditions. These clouds, known as cumulonimbus when they develop into thunderstorms, can reach significant heights and indicate strong upward air currents. As a result, they often lead to severe weather phenomena such as heavy rain, lightning, and even tornadoes. Their appearance in the sky is a clear indication that one should be cautious of potential storm activity in the vicinity.
For context, clear skies are generally indicated by the absence of cloud cover or by the presence of stratus clouds, which are low and flat. High wind conditions are not specifically indicated by the presence of tall cumulus clouds but can occur with various cloud types. Similarly, stable weather patterns are usually associated with lower, flatter clouds, which do not carry the same risk of severe weather as tall cumulus clouds do.