After disrupting some flights in Florida, Georgia and the Carolinas in recent days, heavy rain from Tropical Storm Debby is now causing disruptions in New York and other parts of the Northeast.

On Tuesday evening, moisture from Debby strengthened another storm system that caused strong thunderstorms across the Great Lakes and in Pennsylvania, New York and New Jersey, according to National Weather Service meteorologist Scott Kleebauer as reported by The Associated Press.

According to FlightAware.com, airlines canceled hundreds of flights Wednesday at airports in the New York area, where there are major hubs at New York’s LaGuardia and John F. Kennedy International airports and at Newark Liberty International.

Atlanta-based Delta Air Lines issued a travel waiver for people with flights booked for Wednesday, Thursday or Friday to a number of airports in the Northeast and beyond, warning that Debby may affect travel to, from or through those cities. The waiver allows customers to change their travel plans and rebook flights to another date without paying a higher fare, subject to certain conditions.

The airports included in Delta’s waiver include: LaGuardia, JFK, Newark, Washington Dulles and Washington Reagan, as well as airports in White Plains and Syracuse, New York; Baltimore, Maryland; Philadelphia, Pennsylvania; Boston, Massachusetts; Hartford, Connecticut; Harrisburg, Pennsylvania; Charlotte and Raleigh-Durham in North Carolina; and Richmond, Roanoke and Charlottesville, Virginia.