UPDATE: South Shore has extended the service suspension through Thursday.

CHICAGO (CBS) — The South Shore Line will not be running any trains on Wednesday, due to electrical problems from the extreme cold.

The commuter rail line ran a test train Wednesday morning, and encountered “significant overnight wire problems.”

As a result, all South Shore Line service has been suspended on Wednesday. Officials will evaluate the weather and operating conditions again on Wednesday before determining whether service will resume on Thursday.

Temperatures had already reached 20 below zero in Chicago by 5 a.m., the coldest it’s been in Chicago in 25 years.