And the rain is not just intense, but comes at inopportune times, said Dennis Todey, the director of the Agriculture Department’s climate hub in Ames, Iowa. Rains are falling hard not in the middle of the growing season, when it could be of the most use, but in the spring and fall, “exactly the time we don’t want more water on our cropland.”

“Almost all farmers agree that they’ve been dealing with much more volatile conditions,” said Mr. Lehman, the Iowa farmer.

Some of the farmers in states like the Dakotas, who planted very late in the season, have already experienced heavy rains and early snows that are further hindering their ability to get crops in. Scott McDougall, who farms wheat, canola, soybeans and corn in Hansboro, N.D., said that he had been spared the drenching in the spring only to have the early snowstorms and unseasonable rains of fall make the fields inaccessible for him and his neighbors. “You couldn’t get into your fields,” Mr. McDougall said. “It was just a nightmare.” He said his soybean crop did not fare badly, but “the wheat will be a complete loss.”

Beau Bateman, a farmer near Grand Forks, N.D., said he saw signs of climate change in farming’s problems. “We’re seeing more extremes than we’ve encountered before,” he said. After the wettest September on record, the soil has become so saturated that it won’t support heavy equipment like combines and beet harvesters. “ They sink in and get stuck,” Mr. Bateman said. His farming cooperative, he added, had nothing but trouble getting its sugar beets out of the ground. “We were only able to harvest two-thirds of our crop.”

Dr. Irwin of the University of Illinois said that the year’s planting had been further complicated by confusing messages from Washington, including an offer of aid to farmers from the Agriculture Department in May to help them deal with the effects of trade tensions with China with $16 billion in price supports if they planted crops. The announcement came later in the year than farmers in many areas usually plant, but hard-pressed farmers decided to try to get the benefits of the program and planted anyway. Dr. Irwin estimated that at least five million acres were planted under risky conditions. “It turned out to be a really bad bet,” he said.

A big reason for the bad outcome: Corn that got caught in the October rain and snow can’t be put in silos until it has been dried somewhat. Under good conditions, it dries in the field, but this year much of it has to be dried with heated air — something that cost farmers dearly, especially with spiking prices for propane. “This is adding stress to an already stressed community,” Dr. Todey said.