Forecasters warned farmers in California's Central Valley to prepare for another night of freezing temperatures late Wednesday and early Thursday.

With a high pressure system keeping the humidity low and the skies clear, the National Weather Service issued a freeze warning from midnight Wednesday until 9 a.m. Thursday for the Central and southern San Joaquin Valley.

Temperatures were expected to dip below 30 degrees overnight, with the coldest locations getting as low as 25 degrees, forecasters said.

The latest warning comes after Central Valley citrus growers appeared to have escaped with little or no crop damage after a string of unusually cold nights.

Officials with the citrus growers association, California Citrus Mutual, said temperatures late Tuesday and early Wednesday were not low enough over a long enough period to cause significant damage.

Prolonged temperatures in the mid-20s can damage citrus crops.

Growers ran wind machines and water to protect crops, Citrus Mutual's Paul Story said. The coldest temperatures also were recorded outside prime citrus-growing areas.

For the rest of the week, fog could develop overnight, which could keep overnight temperatures from dropping as low, forecasters said.