Natural-gas prices jumped about 2 percent Thursday after the U.S. government reported a bigger-than-expected decline in inventories and forecasters said January could be the coldest month in the United States since 1985. Natural gas, used to heat homes and generate electricity, is still at higher levels than the five-year average, but the Energy Department said that supplies are dropping as homeowners and businesses use more to heat buildings. Weather forecasters said a wave of Arctic air will sweep across the United States, starting at the end of this week. The department's Energy Information Administration (EIA) said natural-gas inventories fell by 135 billion cubic feet last week, putting the storage level 1.5 percent below last year's level and 6.5 percent above the five-year average. Prices jumped immediately after the EIA report. Natural gas for February delivery rose 10 cents, or more than 2 percent, to $4.54 per 1,000 cubic feet by midday on the New York Mercantile Exchange (Nymex). Meanwhile, oil prices fell as the U.S. dollar gained versus other major currencies. Oil, which is priced in dollars, tens to fall as the U.S. currency rises and makes crude contracts more expensive for investors using foreign currency. February crude futures were down nearly $2, or about 2 percent, to below $89 a barrel on the Nymex. U.S. retail gasoline prices continued to rise, with the national average increasing overnight to $3.08 a gallon (3.8 liters), according to three price-tracking organizations. Gasoline is now 12 cents higher than a month ago and 39 cents above a year ago.