A heat dome is peaking over the western US and northern Plains, driving record and near-record temperatures that threaten about 40M people and raise wildfire danger.The National Weather Service reports widespread highs of 105 to 115 degrees Fahrenheit, with Billings and Salt Lake City reaching about 109 degrees; Montana faces possible all-time highs and extreme-heat warnings cover multiple states as the peak approaches.Officials say heat waves cause more deaths in the US than hurricanes and floods, warn that extreme heat could hamper efforts to fight large fires in Colorado and Utah, and link the surge to human-driven warming from burning coal, oil and gas.