The grain was "1.2 times oversold" even heading into Thursday, according to US Commodities.
Leaving it, well, Chicago's July contract experienced a late nose dive to close down the exchange maximum of $0.20 a bushel, or 6.2%, at a three-month low of $3.05 a bushel.
The pattern of late decline was a common one in Chicago, even if the extents were less stark in other grains.
That said, the lot did rebound to $5.82 a bushel as of 14:00 Chicago time (20:00 UK time) at the end of the after-hours 45 minutes of dealing, under Chicago's new regime, trimming losses to 3.6%.
The December contract was 1.3% down at $5.16 a bushel.
The grain was weakened initially by poor US export sales data for the week to last Thursday which, at some 480,000 tonnes old crop and new combined, came in well below market forecasts of up to 1.3m tonnes.
Benson Quinn Commodities, terming the data "poor", said that "the reality of these numbers is more of an indication of a lack of demand at the high side of the recent range".
However, the slide was accelerated in later deals by a sell-off seen as down to forecasts putting more rain into the US outlook.
"I turned back to my computer, and the market had puked all over the street," Jerry Gidel at broker Rice Dairy said, noting midday forecasts showing a "little bit more rain in the north areas of the Midwest".
He added: "It is the Wednesday-to-Friday period next week people are shooting at for a big rain event," to erode concerns over dryness which have been creeping into the Corn Belt as they have into the southern US Plains and parts of the former Soviet Union too.
As ever with weather outlooks, involving more than one model, unanimity was not a feature.
"There is certainly disagreement in the amount of rain that will be seen next week in the Corn Belt and the Plains," Darrell Holaday at Country Futures.
But a spike in volumes after midday does hint that weather outlooks at the time were to blame for the drop in prices.
US wheat export sales, at more than 800,000 tonnes, were well above expectations – and in a period during which prices were soaring – although all but 72,000 tonnes were for new crop, a signal perhaps that, with Russia dryness fears in the ascendancy, buyers thought it wise to get a little long-term cover.
As an extra support, results from the early harvest in Kansas, the top US wheat producing state, are disappointing some observers.
"Wheat yields are coming in from Kansas at 40-50 bushels an acre, which are below levels expected a few weeks ago," Paul Georgy at Allendale said.
Furthermore, the IGC cut its estimate for world wheat stocks at the close of 2012-13 to a four-year low, with particular weakness in inventories in major exporting countries.
"This has kept a bid under soybeans during the session," he said.
While there was an early caution, in a report of the cancellation by China of four cargoes of Brazilian soybeans, fuelling speculation of switches, ditches and deferrals which has dogged the oilseed and corn all week, there was little evidence of such behaviour in the USDA report. (Nor for corn either.)
Towards the close, Argentina's Buenos Aires grains exchange cut its estimate for the domestic harvest by 1.1m tonnes to just under 40m tonnes, below forecasts from other major commentators, adding extra support to prices.
The July lot stood at $13.81 ¼ a bushel, up 1.4% on Wednesday's close, with the new crop November contract up 1.5% at $12.76 ½ a bushel.
There was strength among New York soft commodities too, albeit with crops recovering from some depressed, multi-month lows in the last level.
Interestingly, data showed this was one commodity which investors were not losing (largely negative) interest in, with open interest (ie live positions) on Wednesday its highest in nearly two months.
Compare that with grains. US Commodities noted that "open interest was down on corn, soybeans and wheat yesterday. This indicates general commodity liquidation. Funds continue to abandon the markets."
In fact, sentiment was broadly a little better on Thursday, with European share markets closing higher, and the CRB index recovering 0.2% from the last session, when it closed at its lowest since September 2010.
This was one of the factors which helped raw