As drought gripped an expanding area of America’s prime cropland, the spring wheat harvest got under way last week. Markets were on edge over prospects for the corn and soybean crops in view of the brutally hot temperatures and lack of rain. But four-fifths of the nation’s winter wheat crop already was in the bins, and the early start to the spring wheat harvest may allow that crop to escape the worst predations of what analysts suggested was the most widespread severe drought in the United States since 1956.

U.S. Department of Agriculture field offices in the Upper Midwest reported on the early progress of the spring wheat harvest. The South Dakota spring wheat harvest was 12% completed by July 15. The harvest’s start was so early there were no year-ago or five-year comparisons. The winter wheat harvest in that state was 82% completed compared with 15% as the recent five-year average progress for the date.

The spring wheat harvest was 1% completed in both North Dakota and Minnesota on July 15. As in the case of South Dakota, the early starts to the harvest precluded one-year and five-year-average progress comparisons.

Spring wheat condition ratings, while down from late June, have held up relatively well, sustaining hopes the harvest will continue to proceed well ahead of the average pace and be completed before weather has a chance to wreak havoc.

Spring wheat rated in good-to-excellent condition on July 15 was 73% in North Dakota (89% on June 24), 65% in Minnesota (74%) and 55% in Montana (61%). Drought exacted a greater toll on condition in South Dakota, where spring wheat was rated 46% good to excellent on July 15 compared with 71% on June 24.

The U.S.D.A. on July 11 forecast yields of spring wheat other than durum across most of the northern Plains to be higher than a year ago, based on July 1 conditions. It was uncertain whether dry conditions across much of the region since July 1 will take a significant bite out of yield potential. That will become known only as the harvest progresses.

The U.S.D.A. forecast average spring wheat yield in North Dakota this year at 40 bus per acre, up from 30.5 bus per acre in 2011 and compared with 39 bus per acre as the recent five-year average. South Dakota yield was forecast at 35 bus per acre, up from 31 bus per acre in 2011 and compared with 40 bus per acre as the five-year average. Minnesota spring wheat yield was forecast at 50 bus per acre, up from 46 bus per acre in 2011 and compared with 52 bus per acre as the average. And average Montana spring wheat yield was forecast at 30 bus per acre, down from 31 bus per acre in 2011 and compared with 29 bus per acre as the five-year average.