Like the red showing up across weather maps for December, weekly spot gas prices all ended on the negative side of the ledger during the Dec. 7-11 week. Losses were rather substantial, particularly on the East and West coasts, but also in parts of the Southeast.

NGI’s Weekly Spot Gas National Avg. tumbled 20.5 cents to $2.450.

Spot prices were lower at the start of the week as fairly moderate weather blanketed much of the Lower 48. As far south in Texas, crisp mornings led to near-perfect afternoons, limiting the need for widespread heating. By the middle of the week, cash prices had begun to firm amid some lingering cool weather in New England and the threat of a chilly weather system moving into the West later in the week.

However, the rally was not to last, with dramatic...