Northern has issued "essential travel only" guidance due to the heatwave this week.
The rail operator is asking travellers in the North West to avoid using the transport if possible, on Tuesday, July 19. The warning is in place due to the weather warning issued by the Met Office.
Chris Jackson, regional director for Northern, said: "Whilst this isn't a 'Do Not Travel' notice - which we have in place across some parts of our network tomorrow - given the guidance published by government and expected disruption caused by extreme temperatures, we would advise customers only to travel if they really have to.