June 19 (Bloomberg) -- Corn rose for a third day in Chicago on speculation that rain and cool temperatures during April and May reduced U.S. planted acreage and cut yield potential. Wheat and soybeans also gained.

Rainfall from March to May in Iowa, Minnesota, Wisconsin and Michigan was the most in 119 years of weather data, the National Oceanic and Atmospheric Administration said in a report. Corn planting on May 26 was 86 percent completed, which may have encouraged farmers to idle land for crop insurance payments or switch to soybeans that can be planted later, according to Greg Grow at Archer Financial Services Inc.

"The focus is on the uncertainty about the number of acres that did not get planted, and the potential yield losses from fields seeded after the middle of May," Grow, the director of agribusiness at Archer Financial in Chicago, said in a telephone interview.

The USDA estimated June 12 that the U.S. corn harvest will rise 30 percent to a record 14.005 billion bushels this year as farmers plant the most acres since 1936 and yields recover from last year's drought. The government will update planted acreage estimates on June 28.

Corn supplies before the harvest are projected at 769 million bushels, the smallest since 1996, after the worst drought in more than 70 years reduced production to the lowest in six years, the USDA said last week

"We have a very tight supply situation ahead of the harvest, and we may not be able to see that type of crop USDA is currently forecasting without ideal-weather conditions the next three months," Grow said.

David Fuller's view We had some record plantings in the US but so much can go wrong during a crop season. Weather conditions in particular have become more turbulent.

I have used the actual yearend contracts because the usual 1st month continuation charts had some sharp drops as the last contract expired, and this distorted the picture. Nov soybeans (weekly & daily) led the recovery with a surge last month. Today's action suggests that the current pattern could be a bullish consolidation and a close beneath $12.75 would be required to question seriously this hypothesis. Dec corn (weekly & daily) now shows clear evidence of base formation development and a close beneath this month's low would be required to suggest otherwise. Dec wheat (weekly & daily) is lagging but today's upward dynamic from the range lows has at least temporarily reaffirmed support just beneath $7.

While weather conditions between now and the harvests will continue to remain the overwhelmingly dominant influence on these contracts, upside follow through would begin to put some upward pressure on food prices. Conversely, near perfect crop conditions are now required to reverse recent gains and lower food prices.