Livermore Valley grape harvest begins ahead of schedule due to warm weatherGrape harvest season is underway in the Livermore Valley earlier than usual as warmer weather has accelerated the ripening process, giving wineries a shorter window to bring in their crop. Grape harvest season is underway in the Livermore Valley earlier than usual as warmer weather has accelerated the ripening process, giving wineries a shorter window to bring in their crop. Grape harvest season is underway in the Livermore Valley earlier than usual as warmer weather has accelerated the ripening process, giving wineries a shorter window to bring in their crop. LIVERMORE, Calif. (KGO) -- Grape harvest season is underway in the Livermore Valley, with at least one winery beginning its harvest earlier than usual as warmer weather has accelerated the ripening process. Amos said he expects the harvest season to last two to three months, though in some years, grape picking continues through Thanksgiving.