FRESNO, Calif. A cold snap that has California farmers struggling to protect the $1.5 billion citrus crop has slowly started to ease.
For a fifth night, temperatures in the San Joaquin Valley, the state's agricultural heart, dipped as low as 21 degrees.
Prolonged temperatures in the mid-20s or below cause damage to citrus crops.
In urban centers, it was 39 degrees in downtown Los Angeles early Tuesday, while San Francisco had 37 and San Diego, 36.
Motorists were urged to use caution because of icy conditions in some places. Black ice was blamed for a seven-car pileup in Oakland Monday and other crashes elsewhere.
Several Lake Tahoe casinos are cleaning up after below-zero temperatures burst sprinkler pipes.
In New Mexico, some public facilities opened later than usual Tuesday because of winter weather conditions that included freezing temperatures and poor driving conditions.
High pressure is nosing into the west over the next couple of days, and Southern California will start warming up, CBS Los Angeles reports. Temperatures could hit 70 again by Wednesday.
On Monday, some California citrus growers reported damage to crops and an agriculture official said national prices on lettuce have started to rise because of lost produce in Arizona.
"I think mandarin growers are going to see a range of significant damage, enough that they will have to separate their crops," said Paul Story of Exeter-based California Citrus Mutual, an association of the state's 3,900 citrus growers.
Mandarins are more susceptible to cold than other citrus and start to freeze at about 32 degrees, Story said. Because many mandarin trees were planted in recent years as the fruit's popularity soared, they are grown in colder areas outside the traditional citrus belt.
Other citrus crops saw little or minimal damage, Story said. This year's high sugar content in oranges helped protect them, he said, because sugar inhibits freezing.
Growers deployed wind machines to keep the warm air closer to the ground and irrigation to raise the temperature in the groves. Rows farthest away from the protection could be damaged, Story said. And farmers who do not have wind machines could lose crops.
Lindsey-based Robert LoBue who grows 1,000 acres of citrus, including mandarins said wind machines were critical in his groves, but saving the crop doesn't come cheap. LoBue runs one wind machine for every 10 acres and has to employ a crew to operate them.
"We're very diligent, we run the wind and water all night," LoBue said, "but we're spending thousands of dollars to protect these crops."
The freeze warning was to remain in effect until 10 a.m. Tuesday for central California.
In Southern California, where strong winds helped keep some crops out of danger by keeping the cold from settling, farmers said any damage would negatively impact workers and consumers.
"We have between 170 to 200 employees and if we can't pick we have to lay off our picking crews," said John Gless, a third-generation Riverside-based grower. And if there's less fruit to pick, he said prices will go up.
To the east, the freezing temperatures already have done enough damage to southwestern Arizona lettuce crops that prices are increasing, said Kurt Nolte, a Yuma, Ariz.-based agricultural agent for the University of Arizona.
The area provides much of the nation's leafy greens during the winter, and farmers are reporting damage to many romaine and iceberg lettuce crops. The cold is freezing the heads of the lettuce and affecting the quality and yield, Nolte said.
The price for a carton of lettuce in Yuma two weeks ago was $7 to $8. As of Monday, it cost around $20 per carton, he said.
"That's a result of cold weather in the Yuma area for the last six weeks," Nolte said.
Overnight temperatures this week have dipped into the 20s around Yuma, and Nolte said lettuce farmers can't protect their crops.
"With lettuce, you don't have the luxury of wind machines to stir up the atmosphere," he noted. "You have to live with what Mother Nature brings. Very little can be done other than maybe running some water to protect what's going to be harvested the next day."
Nolte said Yuma farmers haven't seen much damage so far with other crops such as spinach, cauliflower and broccoli.
Metropolitan Phoenix marked one of its coolest stretches since 1988 and Sunday morning's low of 7 degrees in Douglas, Ariz., broke a record for January in the Mexican border town.
Farther north, a school district on the Navajo Nation cancelled all classes Tuesday because of freezing temperatures.
Temperatures in Window Rock, Ariz., were expected to be well below freezing Tuesday with a high of 21 degrees and a low of minus 5 degrees. The Window Rock School District posted the cancellation notice on its website Monday, saying heating the schools has been a problem.
In Nevada, the temperature in Ely plummeted to 24 below zero early Monday and wind chills were expected to drop to near 40 below into Tuesday.
And in northern New Mexico, parts of Interstate 25 and some other highways were snow packed and icy Monday, and officials warned travelers that additional light snow could lead to hazardous driving conditions when coupled with the freezing temperatures.