Nov. 6 (Bloomberg) -- Cotton output in the U.S., the largest cotton exporter, probably will be less than forecast in October after excess rain last month threatened crops in the most-productive growing regions, analysts said.

The U.S. Department of Agriculture’s forecast may fall 2.3 percent on Nov. 10 to 12.7 million bales for the 12 months through July, based on the average projection of eight analysts surveyed by Bloomberg News. Last month, the USDA estimated output at 13 million bales.

The decline is “mainly because of wet weather in the Delta states,” Carl Anderson, a cotton economist and professor emeritus at Texas A&M University in College Station, said by e- mail. “Boll rot and seed sprouting in open bolls reduces yield.”

Cotton futures have climbed 38 percent this year on concern U.S. output may decline. Futures for December delivery slid 0.7 cent, or 1 percent, to 67.41 cents a pound yesterday on ICE Futures U.S. in New York.

Excess rain threatens to damage unharvested cotton in open pods, or bolls, leaving the fiber exposed to moisture. Bolls were open on 92 percent of plants in the week ended Nov. 1, up from 91 percent a week earlier, the USDA said on Nov. 2.

The Mississippi Delta region, which includes Arkansas, Mississippi and Louisiana, had “extremely heavy” rainfall last month, according to Dale Mohler, a senior meteorologist for AccuWeather Inc.’s Web site.

Six Times Normal

About 12 inches (30 centimeters) fell on average across the northern part of the region and as much as 18 to 24 inches soaked the south, Mohler said from State College, Pennsylvania. That’s as much as six times the normal amount, he said.

“That’s just incredible for one month,” Mohler said.

About 28 percent of the cotton had been harvested in the week through Nov. 1 in the 15 states that produce most of the U.S. crop, the USDA said on Nov. 2. That compares with the average of 50 percent at the same time of the season in the past five years, government figures show.

Temperatures sank below freezing last month in parts of West Texas, the most-productive region in the biggest-producing state, Mohler said. The condition of the crop worsened, with 42 percent rated good or excellent in the week through Nov. 1, down from 44 percent in the previous week, the USDA said.

The department may cut its cotton-export forecast to 10.4 million bales in the year through July, the analysts estimated, on average. Last month, the department forecast shipments of 10.5 million bales. A bale weighs 480 pounds (218 kilograms).

Export Forecast

In October, the USDA said U.S. growers collected 12.82 million bales of cotton in the 12 months through last July. Traders in the U.S. shipped 13.28 million bales in that period and had 6.34 million bales in warehouses on July 31, the government said last month.

The USDA’s inventory forecast for the current marketing year will drop to 5.3 million bales from 5.4 million estimated last month, according to the analyst survey.

The department’s estimate of world production may fall to 102.2 million bales from 103.78 million projected last month, according to John Flanagan, the president of Flanagan Trading Corp. in Fuquay-Varina, North Carolina. Estimated world mill use may rise to 113 million bales, he said, from 112.64 million forecast in October.

To contact the reporter on this story: Elizabeth Campbell in New York at ecampbell14@bloomberg.net

Last Updated: November 6, 2009 00:00 EST