LINCOLN, NEB. — Tropical Storm Isaac, which brought heavy rains to parched areas of Missouri, Illinois and Indiana in late August 2012, was the first blow to the fast-developing drought that made history last year, said Brian Fuchs, a climatologist at the National Drought Mitigation Center at the University of Nebraska.

After that, more moderate temperatures, regular precipitation and a normally cold winter, followed by a cool, wet spring, made for a very different growing season in 2013.

This year, small percentages of the corn and soybean crops never made it into the ground because planting delays caused by excessive rainfall lasted long enough to hit “prevent plant” dates, after which yields were expected to be sufficiently reduced that it was wiser to abandon those fields for crop insurance.

Despite the wet conditions and reports of unplanted fields, the U.S. Department of Agriculture, in its June 28 Acreage report, estimated that 97.4 million acres have been planted to corn in 2013, a slight increase over 2012. Soybeans were expected to be planted on a record high 77.7 million acres, up 1% from last year, even though the U.S.D.A. noted that “Planting conditions this spring were much worse than last year as cool and wet conditions delayed planted in many areas of the Corn Belt and Delta.”

Despite the almost complete mitigation of drought in the central swath of states , the U.S.D.A. as of June 2 rated less of the 2013 corn crop in good-to-excellent condition than last year at the same time: 63% in 2013 compared to 72% at the end of June last year. But those numbers had changed dramatically a month later when good-to-excellent ratings as of June 30, 2013, were 66%, compared with 48% a year earlier and reflecting the onset of the drought last year.

Droughts are defined as prolonged periods of insufficient precipitation that become severe enough to impact crop development, water supplies and the natural environment. No one knows how long a drought will last but there is a general belief that the bad ones can last for significant lengths of time. The Dust Bowl persisted for a good portion of the 1930s, for instance.

But the multi-year scenario failed to prevail in 2012 and the worst drought in 50 years faded in one year. Yes, there was localized drought in Texas and Oklahoma in 2011, but Mr. Fuchs said those conditions were part of their own distinct weather system. And there are remains of last year’s drought in exceptionally dry portions of Colorado, New Mexico and Arizona, but most of the interior of the United States now has adequate to surplus soil moisture.

Mr. Fuchs said snowstorms in March and April of 2013 started the process of replenishing soil moisture. That was followed by plentiful rains — too plentiful in some areas — that left Iowa with a record amount of precipitation — more than 16 inches — for any spring since record-keeping began more than a century ago.

The weekly map of patterns of precipitation from the U.S. Drought Monitor looks starkly different at the start of July 2013 compared with a year ago. From the western borders of Minnesota, Iowa, Missouri, Arkansas and Louisiana all the way to the Atlantic Ocean, there is virtually no drought. Last year, the July 3 Drought Monitor map of the United States reported some level of drought in parts of every state in the lower 48 except extreme northern New England.

As for the Corn Belt, “we were in a different cycle (in 2013)” where one or two rain events gave way to the stacking of one onto the other, Mr. Fuchs said. He didn’t have a name for the cycle and said the recovery from the drought of 2012 couldn’t have been predicted.

The path of the Missouri river was a pretty good indicator of “the haves and the have nots” of sufficient rainfall this year — areas east of the Missouri had adequate to excessive soil moisture, he said, while those on the western side still might be grappling with some level of excessive dryness.

In the unpredictable world of weather, what’s needed now, Mr. Fuchs said, is some warmer weather to help crops catch up since they are now mostly at least a week behind average.