By 6:10 a.m. Thursday, Amtrak had canceled 18 Northeast trips, including six Acela services and trains 72, 74, 76, 73, 75, 77, 84, 119, 173, 176, 193 and 196.
Forecast temperatures prompted the railroad to impose heat restrictions from 11 a.m. to 7 p.m. Wednesday through Saturday, warning trains may run at reduced speeds and face delays.
Amtrak said excessive heat can expand rails, bridges and overhead wires, creating safety risks that require locomotive engineers to slow trains as a precaution.
The disruptions hit the busy Northeast Corridor ahead of the July 4 holiday, with Amtrak saying it will keep monitoring conditions and update affected customers.