Kay was born Catherine Mary Rhoads on January 16, 1914, in Los Angeles, California. She spent part of her childhood in Ohio, where her father was from, before returning to California with her family at the age of nine. Kay's early life was marked by health challenges, including a near-fatal bout of pleurisy at the age of six and recurring illnesses throughout her teenage years. Despite these obstacles, she pursued a career in modeling and acting, eventually breaking into film in the mid-1930s.
Kay's early film roles included appearances in feature-length dramas and musicals, such as Broadway Melody of 1936 and Strike Me Pink. She also appeared in several serials, including The Vigilantes Are Coming and Radio Patrol, and co-starred with actors such as Robert Livingston and Gene Autry in westerns like The Three Mesquiteers and Ghost Town Gold.
In the late 1930s, Kay's career began to slow down, and she eventually broke her contract with Republic Pictures to join Universal. She continued to appear in films throughout the 1940s, including the westerns Riders of the Badlands and Enemy of the Law, but her roles became increasingly secondary.
After marrying an MGM still photographer and having two children, Kay's career came to an end. She was divorced twice and remarried twice more, eventually moving to the mid-West and then Reno. Kay spent her later years in Desert Hot Springs, California, where she underwent heart surgery in 1997 and passed away the following April at the age of 84.
