Were they in a drought region?

From my past family farm experience,  extremely hot temps and good overnight or morning rainfall made our corn grow like mad.   We had a picture in the local paper for one insane crop where they were 10 feet tall.  

So if its hot, its ok if they get precip.

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Its all about population!

It is also about rest period for the crop.  Sustained high night temperatures negatively impact yield through increased respiration.

In Iowa our recent heat wave has lasted less than a week and we have had rain.

Also don't forget that the crop genetics and weed control are also much improved over 1930.

And, of course, even if feeding the world were simply a production issue, this technology would fail, as Duffy's findings show. GE crops are not increasing yields and nor are they benefiting farmers financially by reducing their costs. Those who support GE crops are, therefore, revealed as principally supporting the profits of the biotechnology industry.

Contrast the failure of GE crops with the viability of non-GE alternatives, as has been demonstrated for example in a review of 208 projects from 52 countries, adopted by 8.98 million farmers on 29 million hectares of land in Asia, Africa, and Latin America. Pretty, J. and R. Hine (2001) Reducing food poverty with sustainable agriculture: a summary of new evidence, Occasional Paper 2001-2, Centre for Environment and Society, University of Essex,
.

Using a range of sustainable agriculture technologies - none of which involved GE - farmers have achieved yield increases of 50-100% for rainfed agriculture, and 5-10% for irrigated crops.

I can back this up with data I've seen (at the USDA). During the 1990's, GE cotton replaced old standby cotton strains throughout the southeastern United States, some dating back to the early 20th century.  Widely promoted as a means to improve yeilds and reduce production costs, by the late 1990's GE'd cotton strains made up 80%+ of planted varieties, as the two principle companies that produced these seeds slowly acquired or drove out of business the smaller, independent non-GE seed companies.
The GE seeds could not legally be saved, a liscensing fee was assessed on top of the cost of the seed, and the primary advantage of the GE'd strains were that they were resistant to a petrochemical-derived herbacide (weed control) called "Roundup", which just happens to be manufactured by the same company (Monsanto) and/or certain insects.
The Roundup you buy in the hardware store is 1/10th strength of that used on farms.

Turns out that the roundup ready cotton was extremely succeptible to drought, which we here in the southeast have experienced in abundance for 8 of the last 10 years. Average crop yields per acre fell, rather than rising, compared with similar fields (and even test plots) planted with old strain, non-GE cotton. A class-action lawsuit was pending against Monsanto when I left the USDA. I doubt it had meaningful results.

In England, we have had extreme heat (for us) and drought conditions. The farmers have bought in the crops several weeks early and in much smaller quantities as the wheat grain did not grow because of lack of water. Crop yields are down on a typical year due to the heat and drought.