YORK train passengers are being warned to travel only if absolutely necessary on Monday and Tuesday - because speed restrictions and disruption are likely in the heatwave.

Network Rail says response teams will be deployed to mitigate the impact of the extreme heat where possible but there will be delays and cancellations to train services due to the unprecedented heat, with a risk of rails buckling and overhead wires hanging too low and getting caught by trains.

A spokesperson said steel rails absorbed heat easily and tended to be about 20 degrees above the surrounding air temperature, and when steel became very hot it expanded, and rails could bend, flex and, in serious cases, buckle.

They said overhead electric lines which power some trains on the East Coast Mainline were also susceptible to faults in extreme temperatures when the steel wires overheated, which could cause them to hang too low and increase the risk of getting caught on passing trains and knocking out the electricity supply.

Passengers who do decide to travel are being told to remember to bring a water bottle with them, which could be refilled for free at most Network Rail's managed stations, and to allow considerably more time to complete their journey.