NEW YORK—Corn prices jumped Monday as investors bet that more rain in Midwestern states will force farmers to plant less of the crop, tightening supplies and adding to growing food costs for consumers and livestock owners.

Other commodities traded mostly higher, with crude oil rising to a trading record near $120 and gold, silver and copper also gaining.

Corn prices have shot up 26 percent this year amid dwindling stockpiles and surging demand to feed livestock and make alternative fuels such as ethanol.

But the weather has been the biggest factor in recent ...