Joel 3:13

3:13 Like grain ready to be cut down with the sickle (Is. 17:5) and like grapes waiting to be pressed (Is. 63:3), the wicked nations are ripe for a harvest of judgment (cf. Rev. 14:15, 18, 20).

winepress is full . . . vats overflow. The full winepress and overflowing vats emphasize the enormous wickedness of the nations massed in the valley for judgment.