OMAHA (DTN) -- Following a July heat wave that was one for the record books -- accompanied by rainfall that in most of the region was well under 50% of normal -- the central Corn Belt goes into the home stretch of row-crop season in various stages of drought.

The early-August findings by the National Drought Monitor show more than 70% of both Indiana and Missouri with either "abnormally dry" or "moderate drought" conditions in effect, 61% of Illinois in those two categories and almost 45% of Iowa with these conditions.

"I am amazed by what's happened," said Illinois state climatologist Jim Angel. "The beginning of July, everything's going great. Now, six weeks later -- wow -- we went from very good to very bad in a short order."

Angel said that the Midwest has had a "flash drought" -- where intense heat combined with very dry conditions produces the same impact that a more typical drought takes months to develop. "The usual drought formation is over a three-to-six-month timeframe. But this year, it basically stopped raining July 1 with that heat wave adding to it. So, we had the drought develop over the course of four to five weeks. If temperatures would have been a little milder, or precipitation a little more generous, this probably wouldn't have happened."

Telvent DTN Senior Ag Meteorologist Mike Palmerino attributes the Midwest flash drought to the influence of the historic, almost year-long drought that has gripped the Southern Plains.

"I think it was certainly an expansion of that Southern Plains drought," Palmerino said. "It really hit Missouri hard and then a tongue of that swept out into central Illinois and central Indiana."

The flash drought's effect was one reason cited for USDA predicting a nationwide corn yield of 153 bushels per acre in its August production estimate, a decrease of almost six bushels an acre from the agency's projections in July. That nationwide average included a 177-bushel-per-acre yield for the state of Iowa, a number that Iowa State University extension agronomist Roger Elmore thinks will probably decline in later estimates as a result of the flash drought.

"That yield (177 bpa) is in my calculations right at trend line," Elmore said. "I would expect that Iowa will have closer to the 2010 yield than to that trend line. It's because of that heat that we had in July and early August."

If that's the case, Iowa's yield is likely to see close to a 10-bushel-per-acre drop from USDA's August estimate. In 2010, Iowa's corn yield was 165 bushels an acre. But Elmore is not surprised at that prospect.

"If we don't get some measurable precipitation soon, we'll see drought stress, starting with the coarser soils first and then moving into higher-quality ground," he said. "But, rain would still help corn. Even at the dent stage, there is still 50% of the crop's dry matter to accumulate, because you've got some 30 days of fill left."

Despite a round of moderate to heavy rain moving through western Iowa Tuesday morning, Telvent DTN's Palmerino is concerned about less-than-general coverage of rain systems in the Corn Belt. "It depends on the timing of when cool fronts come through," he said. "If a front comes through in late morning through mid-afternoon, that's when it's least active (in producing rain). Evening or overnight usually brings a better chance for meaningful rain."

One feature of this year's flash drought is that its effects, while widespread in the Midwest, will likely have a variety of appearances.

"This is not like the drought back in 1988 where everything was horrible," said Illinois state climatologist Angel. "The story this year is that this drought is so short and intense that there will be different individual stories based on soil types, planting dates, and even farming practices."

Bryce Anderson can be reached at bryce.anderson@telventdtn.com

(AG/SK)

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