Worldwide Markets Roiled by Data-Center Snafu in Chicago Suburb

One of the first signs of trouble arrived at 9:41 p.m. Eastern time on Thursday, when most of Wall Street was shut and traders were still enjoying the Thanksgiving holiday in the US.

“Due to technical issues,” CME Group Inc. said in a one-line email to clients, its futures and options “markets have been halted.”

The problem, it turned out, was the cooling system at a data-center complex in the suburban town of Aurora, Illinois, some 50 miles (80 kilometers) from Chicago, which serves as the main hub for trillions of dollars of derivatives traded each day. Inside, temperatures soared ...