Metra officials are already warning riders that Monday's commute could be a mess because of the expected subzero temperatures.
The rail transit agency issued a statement Friday warning riders that they should "allow extra travel time" because trains will be operating at reduced speeds to reduce stress on rails, ensure switching equipment is working properly and allow time for slower boarding.
Earlier this year, Metra was hobbled by cold weather that wreaked havoc on switching equipment. Riders were stranded at stations and several runs were canceled. Union Pacific officials apologized to commuters in the wake of the last cold blast.
The National Weather Service is predicting a high of zero on Monday and temperatures are forecast to remain below zero Tuesday in Chicago. The suburbs will likely be colder.
Metra officials said extra "engineering and mechanical personnel" will be in the field to keep switches operational and have trains ready for service. They are urging commuters to check the agency's website for service updates at the start of next week.