Sommer was born in Turek in Poland in 1928. He came from an Orthodox family. His parents were Josek and Regina.
He was deported to the Auschwitz-Birkenau concentration and extermination camp with his older brother Mendel. In January 1945, he was transferred to the Buchenwald concentration camp in Germany.
He was finally liberated by the Red Army in the Theresienstadt ghetto in Czechoslovakia in May 1945.