Will this Tuesday prove a turnaround one?
Tuesdays have a habit in Chicago of bringing reversals to a strong trend in the previous session.
That would imply a retreat in corn and soybean futures, after the strong rises in the last session on concerns that a Midwest heatwave will cut yield potential.
And it is easy to see why investors might be tempted to take profits, after a jump of more than 7% in December corn futures in three sessions, and a rise of 8% in November soybean futures in two, taking nearly to 20% their rebound from a multi-month low on August 7.
"Obviously this rally is quite a lot of risk premium to add to the market in such a short time," WxRisk.com said.
"November soybeans went from the yearly lows to the yearly highs in less than three weeks. At some point the market will have priced in enough demand rationing."
However, investors were reluctant, in early deals, to take the idea of profit-taking too far, given the weather threat, and with US Department of Agriculture data overnight showing crop deterioration already last week.
In fact, the proportion of US corn rated "good" or "excellent" fell two points to 59%, in line with expectations and, taken as a whole, the data showed an index figure of 356, in line with that to be expected for late August.
"The average corn crop index for this time of year is 355," Mark Welch at Texas A&M University said.
That said, looking at some of the individual state numbers – Iowa and Indiana ratings down 4 points, Illinois down 5 points and North Dakota down 10 – it is hard to see how the national rating did not drop further.
For soybeans, the proportion of the US crop rated "good" or "excellent" dropped 4 points to 58%, a bigger fall than investors had expected.
That looked more obviously representative of state-by-state data, including a 2-point drop in Iowa, 5-point fall in the Illinois crop rating, and an 11-point drop in Michigan.
"Trade is discussing the possibility of a 40-bushels-per-acre soy yield, which suggests a 200m-bushels-lower 2013 US soy crop than the US Department of Agriculture's August forecast and the need for drastic rationing of 2013-14 US soy supply," Richard Feltes at RJ O'Brien said.
(The USDA has a yield figure of 42.6 bushels per acre.)
And that is "a daunting task, given record US new crop soybean sales of 19m tonnes plus."
Still, "Importantly, there are still three critical weeks remaining during which unfolding weather developments can erode, stabilise or enhance 2013 US soy yield potential".
'Dramatically cooler air'
As for what weather might be in the pipeline, the latest run of the European weather model offered some hope for crop bears, developing next week a "massive trough over the eastern one-third of the country" which will force this-week's hot weather "back into the Rockies", WxRisk.com said.
"This allows for dramatically cooler air for the Great Lakes, the eastern Corn Belt and the east coast and some cooling over the Plains and the western Corn Belt."
However, "the front comes through without any significant rain".
And "the cooling does not last long", with the heat dome "to push east back into the central Plains of the Midwest September 3-4-5".
There was enough to allow December corn futures to fall 1.0% to $4.95 ¾ a bushel as of 09:45 UK time (03:45 Chicago time), but to remain its 50-day moving average at $4.95 ¼ a bushel, which the contract closed above in the last session for the first time in two months.
November soybean futures, offered extra support by the USDA numbers, and particularly sensitive to crop condition at this time of year, eased 0.1% to $13.87 ½ a bushel.
Wheat futures sided more with corn, falling 0.6% to $6.63 a bushel for December delivery, with ideas easing a touch over damage to Argentina's crop from frost.
Furthermore, the condition of US spring wheat improved last week, by 1 point to 67%, and with the hotter weather speeding the spring wheat harvest, which proceeded to 42% complete as of Sunday, up from 18% the week before.
Among soft commodities, cotton eased a touch too, by 0.2% to 84.71 cents a pound In New York for December delivery, after the USDA showed further improvement in the condition of the US crop.
The proportion rated good or excellent nudged 1 point higher in the week to 47%, helped by a sharp recovery in Alabama, which saw an uplift of seven points, to 70% good or excellent.
The Texas crop, the country's biggest, was stable at 35%.