MIAMI (Reuters)—Florida's citrus crop escaped serious damage from freezing temperatures this week but growers were bracing for another blast of arctic air in their groves this weekend, producers and processors said Thursday.

Florida Citrus Mutual, the biggest growers group in the state's $9.3 billion citrus industry, said "some damage" from frigid temperatures had been reported to trees' fruit, twigs and leaves, with 25% of the current harvest complete.

"The bulk of the crop has been spared, this hasn't been a catastrophic event," the group's spokesman, Andrew Meadows, told Reuters, although he said it was too early to be able to venture any detailed estimates.

Florida's citrus industry produces more than three-quarters of the U.S. orange crop and accounts for about 40% of the world's orange juice supply.

While relieved that this week brought no disaster, Florida growers are now fretting over the threat of renewed freeze damage during the nights of this Saturday and Sunday.

Weather forecasters are predicting another pocket of arctic air moving into the southern United States at the weekend, and this could push temperatures again several degrees below the key 28 degrees Fahrenheit level.

Typically, citrus crops get damaged if temperatures fall to 28 degrees Fahrenheit or below for four hours or longer.

"Right now, everybody feels like there hasn't been any extreme damage to the crop," Kristen Gunter, spokesperson for the Florida Citrus Processors Assn., which groups the major juice processors in the state, told Reuters.

"We're looking towards this weekend to see how that shakes out. We're all kind of speculating, just like everybody's speculating, whether it's going to be a destructive freeze or not," she added.

Frozen concentrated orange juice futures in New York rallied this week on concerns over the freeze, and the weather worries are overshadowing the government's scheduled monthly supply report next week on Florida's citrus output.

The U.S. Agriculture Department on Tuesday will release its estimate of Florida's 2009-10 citrus crop. Last month, the estimate stood at 135 million 90-pound boxes, down 1.0 million from the USDA's October forecast.

Harvest going 'hard and fast'

Mr. Meadows, whose group represents around 8,000 Florida citrus growers, said producers would be working throughout the weekend to try to prevent any sustained damage to their trees.

"We're going to be on alert, we're going to be out running water, we're going to be out driving around the groves making sure things are all in order," he said.

Experts say that spraying water on citrus trees just before a freeze kicks in creates a protective coat of ice that actually conserves heat, keeps a tree's temperature more stable and prevents lasting damage from frigid weather.

But such measures imposed additional costs.

"You've got the diesel fuel pumps, that costs money ... you've got labor that you've got to keep on, helping you in the groves ... and that doesn't even account for the emotional wear and tear of having to stay up long hours and worrying about the product," Mr. Meadows said.

Ms. Gunter said the adverse weather also put pressure on the processing industry. "When you have a freeze coming, there's a rush to market where people are trying to get everything off the tree and put in the yards, and that's what going on now."

"It's picked up speed, but we're going ... as hard and as fast as we can, anyway," she said.

But Ms. Gunter added it was always difficult to assess or predict the extent of freeze damage.

"Until the last box is picked, you are never sure exactly what the crop is, so it's hard to calculate damage based on a weather event," she said.