Natural gas futures pulled back from 3 1/2-year highs but held above the psychologically important $5 level Monday on worries that demand this week might be weaker than previously expected.

Natural gas for March delivery fell 11 cents, or 2.1%, to $5.072 a million British thermal units on the New York Mercantile Exchange.

Prices surged 20% last week to trade above $5/mmBTU for the first time since June 2010 as forecasts called for another surge of Arctic temperatures to hit the eastern U.S. in late January.

Natural-gas supplies have fallen below average levels this winter as unusually cold weather has fueled considerable demand for gas-powered indoor heating. About half of U.S. households use natural gas as their primary heating source, according to the U.S. Energy Information Administration.

However, weather forecasts on Monday said that temperatures this week might be less cold than previously forecast, which could reduce heating demand.

The East Coast and South could see warmer weather than previously expected this week, though colder-than-average temperatures are still expected to dominate "over the next few weeks," said Bethesda, Md.-based forecaster Commodity Weather Group LLC.

"The forecast is a bit warmer than when we left the office on Friday," said Bob Yawger, director of energy futures for Mizuho Securities USA Inc. "We're sliding toward $5 here."

However, market watchers still expect a weekly government storage report to show that natural-gas inventories fell by a larger-than-average amount last week, further tightening supplies, Mr. Yawger said.

Natural-gas stockpiles stood at 2.423 trillion cubic feet as of Jan. 17, 13% below the five-year average for the week, according to the U.S. Energy Information Administration. The EIA is scheduled to release inventory data for the week ended Jan. 24 on Thursday.

Continued large withdrawals from storage could keep natural-gas prices elevated above $4/mmBTU even after the cold-weather subsides in the spring, Mr. Yawger said.

Natural gas for next-day delivery at the benchmark Henry Hub in Louisiana recently traded at $5.59/mmBTU, according to IntercontinentalExchange Group Inc., versus Wednesday's average of $5.1853/mmBTU.

Natural gas for next-day delivery at Transcontinental Zone 6 in New York traded between $40 and $150/mmBTU, compared with an average of $59.9819/mmBTU Friday.