A cold front expected to bring freezing conditions into the Valley this week has citrus growers preparing to defend their groves against frost damage.
The National Weather Service in Hanford has issued a freeze watch for Wednesday for the central and southern San Joaquin Valley -- the state's prime citrus-growing region.
Low temperatures are expected to range from 23 to 27 degrees from Wednesday evening through Thursday morning in the coldest rural areas of the region.
Roughly 2% of the Valley's citrus crop has been harvested.
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Citrus industry officials and packinghouse managers say growers have been tracking weather reports and are prepared to use their frost-protection tools, including wind machines and irrigation water.
"We have been watching this system real close, but I think we should be OK," said Bob Blakely, director of grower operations for California Citrus Mutual.
Blakely said there is a slight concern that because the harvest season is off to a late start, a substantial amount of fruit is not ready to be picked and potentially more susceptible to damage if no frost protection is used.
Blakely said growers will turn to wind machines and irrigation water to try to keep citrus grove temperatures above the critical point of 28 degrees.
While citrus can tolerate low temperatures, the potential for damage increases when temperatures drop below 28 degrees for more than three hours.
Mature citrus fruit with a high sugar content can withstand colder conditions better than immature fruit, said Craig Kallsen, a University of California farm adviser in Kern County.
"The weather is probably going to cause some sleepless nights, but growers are well prepared for these kinds of events," Kallsen said.
Tom Wollenman, general manager for LoBue Brothers, a Tulare County citrus packinghouse, said growers will do what they need to protect their valuable crop.
Last year, Tulare County's orange crop was valued at $467 million.
"If we need to turn those wind machines on for a night or two, we will do that," Wollenman said. "This is our first taste of winter weather, and it always wakes everyone up a little bit."
This week will see a transition of cooler to warming conditions. Today's high is expected to be 52 degrees with a low of 34, the National Weather Service said. Along with lower temperatures, there is a 90% chance of rain, said weather service meteorologist Jim Dudley.
Temperatures will continue to drop Wednesday, with a forecast high of 49 and low of 29, Dudley said. When the cooler air sweeps into the Valley from Canada, precipitation will leave.
Thanksgiving will see another drop in temperature, with a forecast high of 47 and low of 31, Dudley said.