Because rails are made from steel, they expand as they get hotter, and can start to curve this is known as 'buckling'. Most of the network can operate when track temperatures heat up to 46°C – roughly equivalent to air temperature of around 30°C – but rails have been recorded at temperatures as high as 51°C.

Train tracks do not literally "melt" like ice, but they suffer from a phenomenon known as "buckling" or "sun kinks" during extreme heatwaves. Most railway tracks are made of steel, which expands as it gets hotter. While engineers leave small gaps (expansion joints) or use "stressed" continuous welded rail to manage normal temperature fluctuations, record-breaking summer temperatures in 2026 can exceed the "stress-free temperature" for which the rails were designed. When the steel expands beyond the physical limits of its fasteners and ballast, the internal pressure forces the track to bend or "buckle" out of alignment. This creates a severe derailment risk, which is why rail operators often impose speed restrictions or cancel services during heatwaves to reduce the additional force applied by moving trains. In some regions, tracks are painted white to reflect sunlight and keep the metal up to 5°C–10°C cooler, but as global temperatures rise, many rail networks are facing the multi-billion dollar challenge of "re-stressing" their tracks for a hotter climate.