With December in sight, the corn harvest is widely regarded as "essentially over," according to individual state-level reports issued this week. There are enough exceptions in the countryside, though, to suggest that a significant amount of U.S. corn remains in the field and may stay there for a while.

In Ohio, 24 percent of the corn crop remains unharvested, and Indiana, Michigan and Pennsylvania all have about 5% left to go.

"Based on November USDA production data, this would amount to close to 200 million bushels," Freese-Notis Weather wrote Monday on Agriculture.com. "That is corn that is not going to see a combine any time soon, given how wet that area is right now, with considerable precipitation, including areas of heavy snow, forecast over the next 24 hours.

Poor drying conditions in the region won't help matters. "Given how poorly soils dry this time of year, for a lot of areas it will probably take frozen ground in order to support machinery in the fields," Freese-Notis said. "It is entirely possible that some farmers may wait until spring to harvest the rest of this year's corn."

Farmers in the eastern Corn Belt confirm this macro view. "It's still corn harvest here in NW Ohio," wrote a farmer in Agriculture.com's Marketing Talk. "The ground is wet.... It will take a freeze now to finish harvest--after the water goes down!"