US natural gas futures edged higher on Monday as optimism around a potential COVID-19 vaccine lifted market sentiment among investors, although forecasts for milder weather and lower heating demand limited the upside.

Front-month gas futures were up 0.5 cent, or 0.2%, to $2.893 per million British thermal units at 9:15 a.m. EST (1415 GMT), after falling for a fifth straight session. The contract touched its lowest since Oct. 20 at $2.821 earlier in the session.

"Gas traders were focusing on modeling the impacts of another round of shutdowns. Pfizer's news announcement this morning has given winter season commodity demand outlooks a much-needed lift," said Robert DiDona of Energy Ventures Analysis.

Pfizer Inc on Monday said its experimental vaccine was more than 90% effective in preventing COVID-19 based on initial data from a large study.

"We expect that last week's seller will be short-covering buyers this week based on headlines. However, without a return to normal or colder-than-normal model outlook, we expect that any rally will be short-lived."

Data provider Refinitiv estimated 216 heating degree days (HDDs) over the next two weeks in the lower 48 US states, well below the 30-year average of 278. Refinitiv predicted demand, including exports, would fall to an average of 91.6 billion cubic feet per day (bcfd) this week from 98.1 bcfd in the prior week.

Gas production in the Lower 48 US states has averaged 88.8 billion cubic feet per day so far in November, up from a five-month low of 87.4 bcfd in October.

The amount of gas flowing to US LNG export plants hit a record 10.2 bcfd this week and was expected to remain near that level in coming weeks after a rise in global prices in recent months prompted buyers in Europe and Asia to purchase more US gas.

In the spot market, mild weather this week cut next-day gas prices at the Dominion South hub in southwest Pennsylvania and Transco Z6 in New York to their lowest since October 2017 and September 2016, respectively.