MEDFORD, Ore. -- An early frost likely to bear down on the Rogue Valley floor has many vintners nervous as they scramble to pick grapes.

Oregon wine country. (File Photo)

A U.S. Weather Service forecast shows nighttime temperatures over the weekend will range from the mid-20s to near freezing.

Grapes will no longer ripen when frost hits.

To complicate matters for the valley's vineyards, a late budding period delayed fruit development, and some growers haven't begun to pick yet.

Dick Ellis, president of the Rogue Valley Winegrowers Association, estimates about 60 to 70 percent of the local growers use frost protection such as wind machines or overhead sprinkling.