(Bloomberg) -- This winter is shaping up to be the costliest for heating in a generation -- especially for households in the US Northeast that must burn oil to stay warm.

With temperatures already dropping, the US has just a 26-day supply of heating oil to draw on, the smallest store for this time of year in at least three decades. National inventories of the fuel are once again at the lowest seasonal point in weekly data going to 1982, according to the Energy Information Administration. 

Spot diesel prices in New York jumped to a five-month high on the data while futures rallied to the highest level since June.

Heating costs this winter are already forecast to be the highest since at least 1997 -- in part because distillate supplies, which include heating oil, are so low. That may not change anytime soon. While profits for producing the fuel are near a record high, the market is in steep backwardation, meaning suppliers lose money if they keep distillates in storage. As of Sept. 30, the US had less than 30 days of supply on hand. 

(Adds details on futures market reaction)

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