The California Citrus Mutual (CCM) has welcomed freezing temperatures that 'blanketed' the Central Valley over the weekend, saying they were a positive change from the unseasonably warm December weather to-date. 

The group said temperatures ranged in the high 20s to low 30s on Friday, Saturday and Sunday nights, adding they were ideal for most citrus varieties at this point in the season.

"Navel oranges and lemons are generally more cold tolerant than mandarin, or easy-peel, varieties such as Clementines, Murcotts, and Tangos, but with frost protection by wind machines the weekend temperatures proved favorable for all varieties," it said.

"The cold weather will actually cause the maturation process of the fruit to slow, allowing for the fruit to store longer on the tree and maintain its flavor, external quality, and color."

It added that in Kern County, a major mandarin growing area, temperatures hovered around 31ºF (-1ºC) on Sunday night, which with the aid of wind machines made for an 'ideal temperature point'. Similarly, in Tulare and Fresno Counties temperatures were well within 'preferable ranges'. 

"Most mandarin growers report running wind machines on average 16 hours this weekend.  Navel oranges, by contrast, can withstand cooler temperatures at longer durations," the CCM said.

"Wind machines were used on roughly one-third of the Central Valley navel crop - covering 44,000 acres - for an average of 5 hours on Saturday and Sunday nights."

Wind machines can raise temperatures as much as 5 degrees (farenheit) by trapping and circulating the warm air rising from the moist ground in the grove. Growers will irrigate in anticipation of cold weather to ensure ground temperatures are warm. When that warm air rises as temperatures cool, it is pushed downward by the wind machines.

The industry body estimates Central Valley citrus growers spent a total of US$25.1 million in frost protection this weekend alone to protect the region's US$2.5 billion crop.

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