Amtrak trains may be delayed this week, because the railroad may reduce train speeds during the day due to scorching hot temperatures.

Through Friday, trains may be delayed between 11 a.m. and 7 p.m. Riders who already have purchased tickets have been notified. Amtrak advised them to check the statuses of their trains in its app or website.

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Dramatic temperature changes can cause overhead wires to expand and contract, potentially leading to system failures, Amtrak officials said. If a wire gets damaged, power must be shut down, and that leads to service delays or suspensions. Rails also can expand during a heat wave and cause misalignment on the tracks. Slowing down puts less stress on the system and helps prevent these issues.

"Heat waves tend to be regional, so the impacts can be huge," Jacob Helman, a former climate consultant at Resilient Analytics, told Grist, a news outlet that covers climate, in 2024. "It can impact the entire Northeast Corridor over the course of five days."

The National Weather Service predicts temperatures to reach nearly 100 degrees on Wednesday, with a maximum heat index of 109 degrees. Thunderstorms with damaging high winds are expected to begin at 4 p.m. "near, north and east" of Philadelphia. The high temperatures on Thursday and Friday are forecasted to be in the mid-to-high 90s.

Also, surface smoke from Canadian wildfires is expected to move into the Philadelphia area on Wednesday and Thursday. It likely will reduce visibility and cause a smell and air quality issues, NWS said.