Theodore Johannes Simons was born in the Netherlands in 1939. He graduated from the Technological University of Delft, where he majored in theoretical fluid dynamics. He was subsequently associated with the North Sea Storm Surge Research of the Royal Netherlands Meteorological Institute and served as a meteorological officer in the Royal Netherlands Air Force.
In 1966, Simons came to the United States as a research student at the Department of Atmospheric Science, Colorado State University (Fort Collins), where he studied atmospheric instability and numerical modeling of atmospheric development. He received his Ph.D. in 1970 for his study of the nonlinear dynamics of cyclone waves.