U.S. natural gas prices slumped to an 11-week low on Monday, as forecasts for mild weather across key consumption regions of the U.S. in the week ahead dampened demand expectations for the fuel. Natural gas for delivery in October on the New York Mercantile Exchange fell to an intraday low of $2.641 per million British thermal units, the weakest level since June 8, before trading at $2.694 during U.S. morning hours, down 0.3 cents, or 0.13%. Natural gas prices lost 8.8 cents, or 3.16%, on Friday to close at $2.697 as warm temperatures in the U.S. Northeast gave way to cooler readings. Demand for natural gas tends to fluctuate in the summer based on hot weather and air conditioning use. Natural gas accounts for about a quarter of U.S. electricity generation. According to the U.S. Energy Information Administration, natural gas storage rose by 53 billion cubic feet last week, below expectations for an increase of 58 billion and following a build of 65 billion cubic feet in the preceding week. Supplies rose by 86 billion cubic feet in the same week last year, while the five-year average change is an increase of 54 billion cubic feet. Total U.S. natural gas storage stood at 3.030 trillion cubic feet, 19.2% higher than during the same week a year earlier and 2.7% above the five-year average for this time of year. Last spring, supplies were 55% below the five-year average, indicating producers have made up for all of last winter’s unusually strong demand. The EIA’s next storage report slated for release on Thursday, August 27 is expected to show a build of approximately 60 billion cubic feet for the week ending August 20. That compares with builds of 77 billion cubic feet in the same week last year, while the five-year average change for the week is an increase of 61 billion cubic feet. Elsewhere on the Nymex, crude oil for delivery in October lost $1.64, or 4.05%, to trade at $38.81 a barrel, while heating oil for September delivery sank 3.25% to trade at $1.415 per gallon.