MTECHTIPS-U.S. natural gas futures extended gains to a second session on Monday, as forecasts showing cooler weather on the way boosted the heating fuel. U.S. natural gas for April delivery rallied 4.3 cents, or around 1.5% to $2.990 per million British thermal units by 9:40 AM ET (13:40 GMT). Cool temperatures will sweep across the Great Lakes and eastern U.S. toward the middle of the week, according to forecasters at Nat Gas Weather.com, with overnight lows expected to drop well below freezing. Temperatures are expected to remain much colder than normal through the end of the week, with highs struggling to reach the 30 s, while overnight lows drop into the teens to below 0F. A fast-moving weather system will then impact the east-central U.S. Saturday into Sunday, followed by warming Monday, but again cooling off mid-week. Prices of the heating fuel are down around 20% so far this year as forecasts for warm winter weather weighed on heating demand expectations. Based on data from the National Oceanographic and Atmospheric Administration, this year’s extremely warm winter has pushed heating demand for natural gas to nearly 20% below average. About half of U.S. homes use natural gas for heating. Without significant demand for natural gas, inventories could stay near record levels and may even continue to pull prices even lower.