NEW YORK, June 25 (Reuters) - Severe thunderstorms threatened mid-Atlantic states on Monday, forcing airports to delay heavily traveled flights between New York and Boston.

Flights to the New York City area from Boston were delayed almost three hours during the morning commuter rush, according to the Federal Aviation Administration, while other flights at Boston's Logan International Airport were delayed almost an hour, it said.

At Newark Liberty International Airport, departing flights were being held on the ground for over an hour "and increasing," according to the FAA.

Arriving flights at Newark and LaGuardia Airport in New York were up to 45 minutes late "and increasing," it said.

The National Weather Service issued severe thunderstorm watches for sections of New Jersey, New York, Pennsylvania and Connecticut, and a severe thunderstorm warning for central Delaware.

"This is a dangerous storm," the NWS said, bringing "damaging winds, large hail and deadly cloud to ground lightning."

Cities bracing for severe storms throughout the day also included Philadelphia, Baltimore, Washington, Norfolk, Virginia and Raleigh, North Carolina, according to Accuweather.com

"In addition to gusty winds, hail and drenching downpours, the strongest storms have the potential to produce a brief tornado," AccuWeather said. (Editing by Ellen Wulfhorst)

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