Weekly natural gas cash prices spiked early in the week as a winter storm system moved across the northern half of the country, dropping chilly rains on the Northwest and heavy, wet snow over swaths of the nation’s midsection.

The blast of winter boosted heating demand Monday and into the following day, establishing a strong foundation that held up through the end of the trading week even as temperatures rebounded after the storms passed.

Production, meanwhile, had recovered late in 2020 from lows earlier in the year amid the coronavirus pandemic and interruptions imposed by a record hurricane season. But output leveled off to start the new year, helping to support prices during the covered week.

NGI’s Weekly Spot Gas National Avg. for the Jan. 4-8 period climbed 18.5...