Whoever first exclaimed “The sky is falling!” must have seen mammatus clouds overhead. Mammatus appear as bubble-like pouches that hang on the underside of clouds. As odd as they look, mammatus aren’t dangerous — they simply signal that a storm may be nearby.
When seen in association with thunderstorm clouds, they’re typically found on the underside of anvils.
Source: Means, Tiffany. “Clouds That Spell Severe Weather.” ThoughtCo, Aug. 1, 2021, thoughtco.com/clouds-that-spell-severe-weather-4089934.