The Metro website said it was a precaution due to the impact of high temperatures on the steel railway tracks.

"The tracks can expand in high heat and we need to run trains at slower speeds to ensure your safety," the statement said. 

"Heat-related speed restrictions come into place when the temperature reaches 38 degrees, causing most services to run behind time. 

"By cancelling trains in advance we are able to manage this and continue to run the smoothest possible service despite the limitations.

"While Friday isn’t expected to reach 38 degrees, we have nonetheless had to plan cancellations on this day, as many of our trains will be out of their normal positions and some are likely to require additional maintenance due to the heat." 

To view the changes to the Bendigo line click here.