A heat dome is set to expand across much of the central United States, pushing temperatures above 100 degrees from Dallas to North Dakota. About 70 million people will face heat advisories. Forecasters say the heat will stretch from the desert southwest to the Gulf Coast and into the Midwest and Great Plains. Some areas, like the Mid-Atlantic and Northeast, won't be hit by such severe weather. The elderly and children are especially at risk of heat-related illnesses. People are advised to seek air conditioning and stay hydrated. Relief might come to the central U.S. toward next weekend.