Corn for September delivery gained 21.5 cents, or 2.7 percent, to end at $8.20 per bushel (25.4 kilograms; 56 pounds), which was an all-time high. December corn rose 20.75 cents, or 2.6 percent, to end at $8.14 per bushel. Soybeans rose 2.6 percent.
Expectations are mounting that harvests will be smaller than anticipated for both crops because of the drought, which covers some two-thirds of the continental U.S. There is little rain in forecasts for August.
Corn fields, particularly east of the Mississippi River, have been hit the hardest. Some farmers are harvesting what they can salvage to sell for livestock feed. Others may forgo harvest and leave the fields alone, analysts say.
Most analysts believe the corn crop is beyond repair now. That is driving up prices because global inventories on hand already are tight.
Soybeans, which are planted after corn, also are suffering the ill-effects of the dry, hot weather. Some analysts think at least a portion of the crop could be salvaged if substantial rain hits within the next couple of weeks, while others think it may be too late.
"There are some areas where those beans are just too far gone, and it's been so hot and so dry it's causing a tremendous amount of stress," said John Sanow, a Telvent DTN analyst.
Global soybean inventories also are low, which is helping keep prices up. Soybeans for November delivery rose 41.75 cents, or 2.6 percent, to end at $16.435 per bushel.
Wheat prices also are increasing on questions about the impact that adverse weather is having on crops in Russia, Kazakhstan and the Ukraine. There also are concerns about India's crop because of a delay in the start of the monsoon rains that help agricultural fields.
September wheat rose 16.5 cents to finish at $9.145 per bushel.
Other commodity prices were mixed ahead of key meetings for the European Central Bank and the Federal Reserve. Traders are hoping the banks will agree on action to promote economic growth.
Gold for December delivery rose $1.30 to end at $1,624 per ounce and September silver gained 53.5 cents to $28.033 per ounce.
September copper fell 1 cent to finish at $3.416 per pound, October platinum rose $3.60 to $1,411.80 an ounce and September palladium increased $16.50 to $588.35 per ounce.
Meanwhile, natural gas futures jumped 6.6 percent on stronger demand. Utilities are buying more of the fuel to generate electricity during the hot summer. Natural gas rose 19.9 cents to end at $3.214 per 1,000 cubic feet. The price in New York has increased 69 percent since hitting a 10-year low this spring.
Benchmark oil fell 35 cents to end at $89.78 per barrel in New York. Heating oil dropped 1.04 cents to $2.8791 per gallon and wholesale gasoline rose 4.9 cents to $2.9368 per gallon.