Dear Michelle Obama, how many guests can you take on your Hawaiian vacation? How about 180 million? The polar vortex spread across the U.S. on Tuesday, with more than 180 million Americans affected and every state except Hawaii experiencing freezing temperatures somewhere. In the Upper Midwest, temperatures are expected to drop to 30 degrees below zero—before wind chill is even factored in. With temperatures as low as -40 in the northern part of Minnesota, Gov. Mark Dayton ordered all schools in the state closed, the first statewide action of its kind in 17 years. “These are temperatures that we haven’t seen for decades,” said Jen Carfagna, a forecaster for The Weather Channel. But the end is in sight: the polar vortex should be moving out by Thursday, with temperatures in the Great Lakes and the Northeast expected to reach the balmy 20s and 30s.