There are castle clouds in the sky and thunderstorms on the ground. What is the castle cloud in this proverb?

There are castle clouds in the sky and thunderstorms on the ground. The castle cloud in this proverb is cumulus. According to the public information of the query, clouds that are higher than stratus clouds and look like cotton piles are called cumulus clouds. Cumulus clouds are usually associated with sunny weather. Cumulus clouds develop into cumulonimbus clouds and form thunderstorms. There are castle clouds in the sky and thunderstorms on the ground. The castle cloud in this proverb is cumulus.