Nov. 21, 2025, 11:50 AM EST / Updated Nov. 21, 2025, 12:14 PM ESTBy Erin McGarry and Kate ReillyA major cross-country storm next week threatens to cause travel delays for millions across the United States during the busy Thanksgiving holiday.Southern California is set to be the first hit, with heavy rainfall throughout Friday. Up to 1 inch of rain per hour is possible, with 1 to 2 inches of total rainfall in urban areas causing localized flash flooding. Rock- and mudslides are also possible.The storm will shift away from California on Saturday and move into the desert, where heavy rainfall is forecast to sweep across southern Arizona. It is then expected to move into the Southern Plains, where it poses the risk of excessive rainfall in areas that were just hit by a separate system over the past two days.By Monday, the rainstorm is expected to stretch from South Texas to the Upper Midwest, bringing pockets of heavy rain and potential flooding that could delay flights.The East Coast is forecast to be affected on Tuesday, with light rain and residual travel delays from the storm.This storm system comes ahead of the nation’s busiest travel period.At least 82 million Americans are expected to travel at least 50 miles from home over the Thanksgiving holiday period from Tuesday, Nov. 25, to Monday, Dec. 1, according to the American Automobile Association (AAA).People with Thanksgiving travel plans should check the weather forecast before traveling and plan accordingly, the National Weather Service said on Friday. Erin McGarryErin McGarry is the executive editor of NBC News’ climate unit. Kate ReillyKate Reilly is a news associate with NBC News.