KANSAS CITY — U.S. grain and soybean futures prices traded higher to sharply higher in overnight electronic trading after disappointing weekend rainfall across parts of the Corn Belt.

Nearby soybean futures traded at the CME Group were up more than 20c a bu, corn futures were up 10c and wheat futures 5c overnight. Driving the markets higher, especially corn, soybeans and Minneapolis spring wheat futures, were disappointing rainfall over the weekend and forecasts for the return of warmer, drier weather this week, according to trade sources. Although the late-planted and slow-developing spring-planted crops needed a boost of warmer weather to promote late-season development, increasing dryness across parts of the Corn Belt and Upper Midwest are a growing concern.

The trade expects weekly crop condition ratings from the U.S. Department of Agriculture, which will be released at 3:00 p.m. Central Time, Aug. 19, will show a slight decline in the good-to-excellent category because of the increasing dryness.

Still, the impact of the dryness is expected to be minimal relative to the widespread 2012 drought, which occurred much earlier in the season.

The U.S.D.A. on Aug. 12 forecast a record large corn crop of 13,763 million bus and the third largest soybean crop of 3,255 million bus. The late-season dryness may trim those estimates slightly, but a record corn crop still is expected.

Despite the large crop forecasts, some soybean futures contracts were up more than 5% and corn futures were up about 2% last week.