In Illinois, for instance, the government reported last week that just 7 percent of the corn crop was planted, far below the four-year average of 48 percent. It's the same story in Iowa, where farmers had planted just 8 percent of its corn, compared with 62 percent a year ago.
The latest Department of Agriculture data showed that just 12 percent of the corn crop was planted on an estimated, record 97.3 million acres. The planting is a three-decade low and compares with a four-year average of 47 percent. But with forecasts for clear skies for the next few days, farmers will work overtime to get seeds into the ground.
The next progress report is released Monday. On Friday, the USDA will release its closely watched World Agricultural Supply and Demand Estimates report, which will provide the first estimate of this year's crop size.
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Technology lets farmers quickly make up for the slow start of planting season, and a big portion of the crop could go in the next week. May 15 is considered a soft deadline for planting, and farmers believe they lose a bushel per acre for every day it is planted after that date.
Mittelstaedt said the biggest single planting progress week was in 1992, when 43 percent of the crop went in one week.
"The modernization and mechanization of American farming and farmers has become so ubiquitous that planting that might have taken several weeks only a decade or so ago can be accomplished in a matter of days now," commodities analyst Dennis Gartman wrote in The Gartman Letter on Wednesday.
Hog farmer David Struthers said that he's having the same experience as many other Iowa farmers. He has planted just about a quarter of his 1,000 acres in Collins, but rain and then 10 inches of snow last week set him back. Struthers, who raises corn to feed his hogs and to sell, said the cool, wet weather is particularly bothersome after the drought. Cool soil prevents the seed from germinating and can cause them to rot in the ground, he said.
"Just now it's starting to get warmed back up to where the temperature would be reasonable to plant," Struthers said. "We need at least three more days of dry weather before we can even get started thinking about planting again, and we've got rain forecast for [Wednesday] and Thursday." He hopes to return to planting by Saturday.
"As a farmer, you've got to be optimistic things are going to get better and you'll do all right," he said, adding that he would not plant after June 1. At that point, the crop would be pollinating during a hotter part of the summer and could risk early frost in September.
"It is raining this morning in Kansas, and that actually shall prove valuable to the winter wheat crop there, but otherwise the skies are reasonably clear; the temperatures are rising and planting is and will be going on apace," Gartman noted.
Corn futures were trading lower Wednesday, at about $6.33 a bushel, about a dollar a bushel ahead of where it was trading at this time last year when farmers had most of their crop in the ground. At this time last year, the unusually balmy spring helped with planting and it was not yet clear the nation was headed for such a serious drought.
"The market sold off mainly because of the improved weather conditions," said Shawn McCambridge, commodities analyst with Jefferies Bache. "But we still need more time. … It will continue to be a factor in the marketplace until we get closer to completed."
Though a hardship to an extent, the wet weather has also helped restore moisture levels in some key planting areas.
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"What it really comes down to is the weather for the rest of the season," McCambridge said. "A couple of years ago, we planted clear into the first weeks of June. That was late, but we had a record yield that year. You can get a good yield even with late planted corn. Last year was near-record planting, the weather went dry, and we had 123.4 bushels yield."
The USDA had predicted that last year's corn crop would yield more than 163 million bushels an acre.
Soybean futures were higher Wednesday on supply concerns. It may be that farmers switch some intended corn acreage to soybeans, which can be planted later.
"If we pencil in something on the order of 96.5 million acres planted and given 'normal' abandonment over time, that shall give us something close to 88.5 million acres harvested and given a national average yield of 153 bushels/acre we shall be talking of a crop of 13.54 billion bushels. … Far more than necessary to meet almost any sort of conjured-up demand for the year," Gartman wrote. "The carryover then is going to grow … materially …and prices then are going to fall … again materially."
Last year's corn crop produced an estimated 10.8 billion bushels, according to the USDA.
Despite the slow start, Mittlestaedt said, "even if we have anything close to the 158/159 trend line, we're going to have a record crop this year barring any major issue."
The highest-yielding corn crop was in 2009-10, which yielded 164.7 bushels an acre.
—By CNBC's Patti Domm