(UPDATED COVERAGE 4:25 p.m.) California’s mandarin and navel orange crops were damaged by a cold blast that sent temperatures into the low 20s in some spots Dec. 5, but the extent of losses may not be known for three to four weeks.

Frost protection measures were successful that day in most areas of Kern, Fresno and Tulare counties, according to Exeter-based California Citrus Mutual. But a sudden drop in temperatures around 6 a.m. worried some growers, and more chill was on the way.

Barney Evans, owner and vice president of sales for Pasadena, Calif.-based Sun Pacific — which packs under the Cuties label — said the mandarins looked intact after two nights of the state’s cold wave, but the worst might not be over.

“It’s way too early to tell,” Evans said Dec. 5. “We don’t see any issues yet. I think we made it through last night okay but I’m very concerned about tonight and the beginning of next week.

“Tonight is supposed to be colder than last night,” he said. “Behind a storm that’s coming this weekend there is supposed to be some critical air mass coming through Sunday night, Monday. All we can do is go to church.”

The National Weather Service issued a hard freeze warning for the San Joaquin Valley through the morning of Dec. 6, and a hard freeze watch for Dec. 8-9. Forecasts for the region called for lows in the low to high 20s on the night of Dec. 5, depending on location.

“There is supposed to be a good inversion tonight, so that could help raise the temperatures anywhere from three to five degrees,” Evans said Dec. 5. “We’re using a lot of irrigation and wind machines. Most of the stuff is ours.”

Frost protection measures can add a few degrees to grove temperatures, and short durations of lows can help. Mandarins require 32 degrees or more; navels, 27 and up. Wind machines had run about 27 hours for mandarins and 12 for navels, California Citrus Mutual reported. So far, growers spent about $6.7 million on protection.

About 85% of the valley’s navels were still on the trees, and 75% to 80% of its mandarins. Previously reported high sugar contents could offer some internal protection.

In Oxnard where California strawberry production centers from December to April, the National Weather Service forecast a low of 34 for Dec. 5. Growers could be spared by their proximity to the ocean, but had frost protection measures ready.

“One grower I talked to had their wind machines in place and they were servicing others in the Oxnard plain to be ready just in case,” Carolyn O’Donnell, communications director for the Watsonville-based California Strawberry Commission, said Dec. 4. “The guys in Oxnard will have temperature sensors that alarm their smartphones to let them know when temperatures do drop enough to institute frost protection.”

Avocado growers in Ventura, Santa Barbara and San Luis Obispo counties had frost protection measures ready if needed, said Tim Spann, research project manager at the California Avocado Commission.

“Most growers know where their cold spots in their groves are, so it’s those historically cold spots we really have to worry about,” Spann said. “There is fruit hanging on the tree for next year’s harvest, and that’s the real risk. The flower buds are still tight; it would have to be a really hard frost, probably down into the teens, to affect them.”

The Salinas Valley also had freezing temperatures. But vegetable production has already transitioned to the Arizona and California deserts.