Amtrak warned that high temperatures could force trains on the Northeast Corridor to be delayed by up to an hour into Sunday evening.
Extreme heat has blasted the Midwest and Northeast this week, with temperatures reaching the triple digits on the East Coast on Saturday and Sunday.
High temperatures make the steel tracks expand, raising the risk of derailments or other track failures. Lowering the speed of trains ensures safety.
The company said delays would slow and end around 7:30 p.m., as temperatures cooled.
Similar delays are common on commuter rail and subway services as well. The Washington Metro slowed trains from a maximum of 65 mph to 35 mph due to the heat, causing slower service.
The heat wave is expected to continue into this week, the National Weather Service (NWS) forecast, with temperatures in the 90s predicted for much of the East Coast.
The Southeast, mid-South and the Plains regions will see the heat wave peak this upcoming week, with the possibility of temperatures exceeding 110 degrees on some days, according to NWS.
AccuWeather meteorologists also predicted that the heat wave would cool off in much of the Northeast on Sunday but could lead to thunderstorms.
“This change in the pattern will first lead to an increase in thunderstorm activity across the Northeast and Midwest regions,” AccuWeather senior meteorologist Brett Anderson said.
“Cooler air will first dip into New England while the worst of the heat gets squeezed into the Middle Atlantic and Southeast,” he added.