(CapitalPress) -A deep freeze that has persisted in the Treasure Valley for most of January has grape growers and wineries concerned about the impact to plants. "I expect some damage. We're crossing our fingers here," said Ron Bitner, owner of Bitner Vineyards in Caldwell in southwestern Idaho. Temperatures have been as much as 25 degrees below normal for the past three weeks and dipped to minus 4 degrees the past three days in Caldwell in the heart of Idaho's wine country. The cold "has been very persistent the last 10 days, with lows between zero and minus 5 the whole time," said Les Colin, a meteorologist with the National Weather Service's Boise office. Colin said temperatures fell to as low as minus 9 in lower elevations in places like Weiser and Ontario, Ore. for a few nights. "That's starting to push the envelope here in Idaho," Bitner said. "It's too early to panic, but definitely there is some concern."