U.S. natural gas prices on Monday extended their remarkable 70% rally from last week as the big freeze pushes heating and power demand to winter records. Early on Monday, the front-month U.S. natural gas benchmark price had jumped by 14% to above the threshold of $6 per million British thermal units (MMBtu) as gas demand surged to very high levels. This was the first time since 2022 that the price of U.S. natural gas has soared above $6 per MMBtu, and nearly double the price at the start of last week. The major storm also led to shut-ins of about…