The U.S. East Coast faces the coldest night of the season as frigid air spills south and threatens agriculture in Georgia, Alabama and the orange crop in Florida.

Freeze warnings were posted by the National Weather Service as far south as the Orlando area, which may be as many as 20 degrees below normal tonight, the National Weather Service said. The advisory alerts growers that subfreezing temperatures are imminent and may kill crops or other sensitive vegetation.

Tampa and others cities in the central part of the state are under a freeze warning from 1 a.m. to 9 a.m. local time tomorrow. Temperatures may fall below 32 degrees Fahrenheit (zero Celsius) for more than three consecutive hours, the National Weather Service in Tampa said on its Web site.

"This is a pretty significant cold snap," Matt Keefe, a meteorologist with Inc. in State College, Pennsylvania, said in a telephone interview. "This could really put a hurting on the citrus crop." He said the jet stream, which normally keeps the coldest air north of the Hudson Bay in Canada, is centered over parts of Alabama and Mississippi. "The cold temperatures could last for a good part of the week," he said.

Jacksonville, Florida, may see a record low tonight, Keefe said. The Miami area will see temperatures 12 degrees to 13 degrees below normal for this time of year, Keefe said.

Tonight will be the coldest and offer the greatest danger of crop damage, Keefe said. The next chance for freezing will come next week.

The U.S. Department of Agriculture last month estimated Florida's orange crop will be 0.7 percent smaller than earlier forecast because adverse weather reduced fruit size.

In New York, overnight lows may be 22 degrees, with wind chills dropping the experience to single digits. Philadelphia may see a low of 20 degrees, Keefe said. Washington may slip to 19 degrees, he said.

To contact the reporter on this story: Dan Hart in Washington at