The man, whose identity was not released, collapsed in his detached garage with a snow shovel close by, Karen Domagalski, operations manager at the Milwaukee County Medical Examiner's office, told ABC News.
It's unclear how long the man was in the garage, Domagalski said.
The autopsy is pending, she said.
This death comes as the Midwest faces a massive winter blast and dangerous temperatures.
Chicago could see a wind chill of minus 50 degrees and Green Bay could see a wind chill of minus 40 on Wednesday.