The United States is getting slammed by a stretch of weather extremes, from flooding rain to record heat and late-season snow. On Wednesday, Washington, D.C., hit a record 86 degrees, then snow fell on Thursday. Meteorologists say the Southwest faces a heat dome with prolonged triple-digit temperatures. Polar cold will push into the Midwest and East. Two northern storms are likely to dump feet of snow, with one strengthening into a rare inland bomb cyclone. Hawaii is dealing with an atmospheric river and flash flooding. Experts link the wild swings to a sharply dipping jet stream.