Natural ice wines require a hard freeze ( −8 °C (17 °F) or colder, and in Germany −7 °C (19 °F) or colder), to occur sometime after the grapes are ripe, which means that the grapes may hang on the vine for several months following the normal harvest. If a freeze does not come quickly enough, the grapes may rot and the crop will be lost. If the freeze is too severe, no juice can be extracted.