Kyle Tapley, a senior agricultural meteorologist, said that as much as 15% of winter wheat plants in the Great Plains could be damaged. Nevertheless, most wheat in the southern Great Plains and Midwest has about 2.5 cm of snow cover which can help to protect dormant crops, he added.

In addition, the USDA revealed that about 62% of the plants were in good or excellent condition at the end of November 2013.

This week, wheat futures traded near the highest level in two weeks.

Wheat futures on the Chicago Board of Trade climbed as much as 1.2% on January 6 to US$6.1275 a bushel, the highest since December 23, 2013, before trading at US$6.0825 on January 7.

The Standard & Poor's GSCI Agriculture Index of eight crops rose 0.1% to 352.58% on January 7 after rising 0.6% the day before. Cattle futures reached US$1.371/pound on the same day, the highest since Chicago trading began in 1964.

"The market is rising on speculation we will see some yield losses that will tighten up US supplies," said Chad Henderson, president of Prime Agricultural Consultants Inc. "We haven't seen these types of temperatures in 20 years, and the market is uncertain of the eventual impact on yields."

"There's some concern over what the cold can do to damage the crops," added Jack Scoville, the vice president of Price Futures Group. "Extreme cold has made logistics a huge problem, and there's some risk in loss of production in both wheat and oranges. The cows and hogs are going to need a whole lot of feed to keep warm."

Meanwhile, livestock slaughter risk delay with increased difficulty to transport animals in the cold, according to commodity broker, Allendale Inc.

The cold weather also means that animals will need to use more energy to stay warm, thus reducing weight increases and potentially limiting beef supplies, explained Rich Nelson, chief strategist at Allendale. USDA data showed that meatpackers processed 15% fewer cattle on January 6 and 26% fewer hogs than a week earlier.

Cattle prices have climbed 1.8% in 2013, the fifth straight annual gain and the longest rally since 1964. Beef output in the US, the largest producer of the meat, may slump 5.7% this year, to its lowest since 1993, based on a USDA projection.

Hard-freeze warnings and watches, which are alerts for farmers, stretch from Texas to central Florida, with 90% of the country to be at or below the freezing mark, according to the US Weather Prediction Center in College Park, Maryland.