Just as another blast of frigid weather swept most of the U.S., propane, the main source of heat for nearly 6 million households, is increasingly hard to find.
The shortage began last fall, when Midwestern farmers depleted stocks of the gas as they rushed to dry an unusually wet corn crop. Supply-chain problems and a surge in exports--in 2013 nearly twice as much propane was shipped overseas, where it commands higher prices, as in 2012--further tightened stocks. Since October, Midwest propane inventories are more than 5 million barrels below average, which has made the fuel scarce from Maine to Alabama.
The...