New crop corn futures soared more than 6%, dragging wheat higher too, as a disappointing weekend for US rain, and forecasts of 100-degrees-Fahrenheit heat, sent investors rushing to reinject wheat premium into prices.
New crop corn for December delivery soared 6.6% at one stage, the contract's best performance in at least two years, after rainfall over the weekend in the US disappointed in many areas.
"Showers developed over the weekend in the Midwest, but rainfall amounts and coverage were way less than expected, mostly just 0.25-0.35 inches in scattered showers in Iowa, Wisconsin and Illinois," Gail Martell at Martell Crop Projections said.
Instead of the "very heavy rainfall" forecast, "showers were light and scattered from a stronger-than-expected ridge of high pressure that stabilised the atmosphere and diminished rainfall.
"This is often what happens in an emerging drought."
'About to turn really hot'
Indeed, the generally low levels of rainfall exacerbated concerns for soil conditions which US Department of Agriculture data show, as of last Tuesday, were in "abnormally dry" or "drought" condition for 60% of the Midwest as of Tuesday, 73% of the High Plains and 74% of the South.
"The longer-term situation still shows precipitation lagging the normal pace, meaning drought conditions of varying degrees still exist from Kansas and Nebraska in the west to Indiana in the east," Paragon Economics and Steiner Consulting said.
"There isn't much subsoil moisture to draw on."
And fears were given further impetus by the prospect of hot weather sapping moisture levels and compromising conditions for the important pollination period.
"Over everybody it is about to turn really hot over the next few days - 100 degrees Fahrenheit heat will surge into Nebraska today," weather service WxRisk.com said.
'Just robbed yields'
At broker Market 1, Mike Mawdsley – while reporting local corn crops as in excellent condition – said that investors were "mindful of how last year heat just robbed yields".
"The next 30 days will see corn in most places either enter or end pollination," a particularly sensitive point in the crop's life-cycle.
Such crop risks contrasted with the December contract's close on Friday of $5.06 a bushel, less than 1 cent from recording its lowest finish in a year.
The contract closed Chicago's electronic trading session at 14:00 local time (20:00 UK time) at $5.35 ½ a bushel, a gain of 5.8% on the close of the last session, helping the July lot add 3.7% to $6.01 a bushel.
While heat is not such an issue for wheat, which is for winter crop largely harvested or for spring crop in areas which have been better watered, futures in the grain were dragged 3.3% higher to $6.29 ¾ a bushel in Chicago for July delivery.