Metro has cancelled six train services this afternoon due to Melbourne's hot weather.

Two outbound services to Pakenham have been cancelled, one to Mordialloc and one to Laverton.

Steel railway tracks expand and can buckle in the heat. Credit:Patrick Scala

Two citybound services, from Pakenham and Laverton, have also been cancelled.

In a statement, Metro said trains were cancelled because of speed restrictions on the network.