A cloud is an accumulation of water vapour in the sky.

Scarce stand the vessels hauled upon the beach, / and bent on marriages the young men vie / to till new settlements, while I to each / due law dispense and dwelling place supply, / when from a tainted quarter of the sky / rank vapours, gathering, on my comrades seize, / and a foul pestilence creeps down from high / on mortal limbs and standing crops and trees, / a season black with death, and pregnant with disease.

Thunder is made from a sulphurous vapour, breaking out of a cloud with lightning, thundering and striking with lightning.

Vapour ascends from water. From it is formed a cloud, and mist near the Earth.