Born in Indianapolis, Indiana, Vonnegut was educated at the Massachusetts Institute of Technology, where he obtained his PhD in 1939. After working in the Research Laboratory of the General Electric Company under Vincent Schaefer (1945–52), he moved to the Arthur D. Little Company and remained there until 1967, when he was appointed professor of atmospheric science at the New York State University, Albany.

In 1947, while with the General Electric Research Laboratory, Vonnegut made a major advance in the rain-making techniques developed by Schaefer, when he found that he obtained much better results with silver iodide crystals for cloud seeding than the dry ice used by Schaefer.