With extreme cold temperatures hitting the Northeast, Amtrak said it will run its trains between Washington and Boston on a modified schedule.

Trains will run with less frequency on the Acela Express and Northeast Regional lines.

Passengers who have paid but decide not to travel today can receive a refund or voucher for future travel. Those with reservations whose trains have been canceled are being re-booked on other trains, but those spots are filling up quickly, officials said.