Clouds (구름, gureum) are read as a symbol of uncertainty and transition — neither the clear favor of sunshine nor the direct message of rain, but the state in between, before it's clear which way things will go.
Clouds covering the sun are read as a temporary obstacle rather than a lasting setback — something blocking your fortune or recognition for now, expected to pass. Clouds parting to reveal blue sky or sunshine is one of the more satisfying favorable sequences in this category, read as a problem finally clearing after a period of doubt.
Riding on a cloud carries its own specific folklore weight in Korean tradition, echoing old stories of immortals, fairies, and heavenly figures traveling by cloud (in stories like 선녀와 나무꾼, the fairy and the woodcutter). This variant is generally read as an elevated, almost dreamlike escape from ordinary circumstances, or a status or recognition that feels above your everyday life.
Dark, heavy storm clouds gathering, even before any rain or thunder actually starts, are read as building anxiety or a difficult period approaching — the clouds functioning as an early warning that lets you brace for whatever the fuller storm dream would represent.