they are usually seen at the base of cumulonimbus clouds (rain clouds).
Mammatus clouds are a type of elongated cloud formation that hangs from the base of the cloud.
These cysts are usually circular or oval in shape and can range in size from a few centimeters to several meters in diameter.
Mammoth clouds usually form in association with thunderstorms or other convective weather. The cold air that follows the storm descends and forms this bag-like cloud layer. They are often seen after the storm has passed.
Despite their ominous appearance, mammatus clouds are not generally a sign of severe weather. However, they may be a sign that a storm has passed and that there may be additional weather activity in the area.