As Chicago is hit with record-breaking low temperatures, workers are keeping the city's commuter rail running by lighting tracks on fire.

A Metra spokesman explained to the Chicago Tribune that the tracks contract in extreme cold, causing breaks in the line.

Workers heat the tracks back up with ropes soaked in kerosene and lit on fire, which causes the steel to expand so that they can be bolt or weld it back into place.

Workers for Chicago's commuter rail system are going to extreme measures to keep the city's trains running in historic cold temperatures.

On Tuesday, Metra workers were seen setting the train tracks on fire, after temperatures dipped as low as -19 degrees Fahrenheit — breaking the city's previous cold weather record for that day set in 1966.

A spokesman explained to the Chicago Tribune that the metal tracks contract in the cold, which can lead to the rails unbolting or fracturing.

A heating system keeps the tracks from shrinking in normal winter weather, but with temperatures well below zero degrees, workers have had to do some additional heating.

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Spokeswoman Meg Thomas-Reile told the Tribune that workers have been laying kerosene-soaked rope next to the frozen tracks and lighting them on fire. Once the metal expands again, workers can go in and rebolt the tracks or weld them back together.

Despite taking these measures, Metra trains were running with delays across the city on Wednesday.

Workers set the tracks on fire in extreme cold to stop the steel from contracting and breaking. Above, workers setting Metra tracks on fire on Tuesday in Chicago. AP/Kiichiro Sato

The Electric Line was suspended in both directions due to wire problems caused by the sub-freezing temperatures, according to Metra's website.

The entire Metra system is running on a modified schedule for Wednesday and Thursday due to the cold.

Meanwhile, Amtrak has suspended all service going in and out of Chicago.

But Wednesday didn't break the record for the coldest day recorded in Chicago, according to CBS 2. That was on January 20, 1985, when the city plunged to -27 degrees Fahrenheit.