'Mists' in the Bible

A day of darkness and gloom,A day of clouds and of thick [dark] mist,Like the dawn spread over the mountains;There is a [pagan, hostile] people numerous and mighty,The like of which has never been beforeNor will be again afterwardEven for years of many generations.

These [false teachers] are springs without water and mists driven by a tempest, for whom is reserved the gloom of black darkness.