Weathermen

Weathermen was the radical leftist faction of Students for a Democratic Society that emerged in 1969, named after a Bob Dylan lyric: "You don't need a weatherman to know which way the wind blows." The group advocated violent revolution and conducted bombings of government buildings.

They later renamed themselves the Weather Underground.

The Weathermen went underground after several members died in an accidental explosion. (Lowercase weathermen are people who forecast weather.)