The Storm Prediction Center has identified the greatest risk of severe storms as stretching over much of Pennsylvania and Upstate New York, with some 6.7 million people in the risk zone.
Environment Canada has issued a tornado watch for Ottawa and much of the surrounding area. The watch is in effect until 9 pm.
A severe thunderstorm watch was posted for much of New Hampshire and western MA until midnight Wednesday morning. The Saranac Lake Volunteer Fire Department, which covers a wide area, reported no calls related to storm damage. Some storms may contain damaging winds and torrential downpours.
Nickel- to quarter-sized hail is possible in areas hit by the strongest storms, according to the weather service.
A few tornadoes will also be possible.
However, embedded supercells within the line of storms could produce tornadoes as well.
The tornado warnings began in the southwestern part of the state around 2:45 p.m., when Yates and Steuben counties were put under a tornado warning, according to the weather service.
It is important to take warnings seriously and seek shelter for the severe thunderstorms.