On Thursday 28th June 2018, as the air temperatures in Cumbria hit the mid to high 20s, the tracks north of Carlisle railway station hit 49 degrees Celsius.
This caused the rails to expand and bend slightly in their settings, as shown in the photograph here taken by a Network Rail engineer.
Ian Joslin, head of Network Rail’s Carlisle delivery unit, said: “We maintain our rails to withstand fluctuations in temperature so they flex as little as possible. However sustained baking by the sun can occasionally lead to steel rails buckling, like they did at Carlisle. When this happens we slow down trains to keep everyone safe.”
Network Rail said that it monitors track temperatures continually, but even more keenly during heat waves.