Flights were grounded on Monday night at three major northeastern airports for significant weather-related concerns. Low visibility at New York’s John F. Kennedy (JFK) airport required a ground stop, while thunderstorms brought operations to a halt at Chicago O’Hare (ORD) and Washington Reagan (DCA).Meanwhile, an active tornado warning was issued for Washington Dulles (IAD) airport and surrounding regions of Washington, DC. As a result, passengers in transit were directed into the underground train station tunnels of the airport until the warning expired at 6:45 pm Eastern.Severe thunderstorms and flash floods were also reported in the Washington, DC, Arlington, VA, and Alexandria, VA regions, and drivers were cautioned to remain off the roads to avoid the possibility of being swept away.The largest airport serving the nation’s capital remains under severe thunderstorm watch, and the tornado and severe thunderstorm warning remains in effect for the greater District of Columbia region, with 70 mph winds and 1-inch hailstones reported from both radar detection and eyewitness accounts.Image by the National Weather Service for Baltimore and Washington DC.The National Weather Service warned that storms were expected to last until 10 pm Eastern, with potential damage from falling trees and large branches.Travelers took to Twitter to notify friends and family of their status, reporting that the airport and airlines were cooperating to keep everyone as safe as possible.Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.Until further notice, travelers are being urged to stay indoors and off the roads unless absolutely necessary.