The 39-year-old actress and 50-year-old actor will reprise April Wexler and Fin Shepard, respectively. The characters are an on-and-off married couple who appeared in Sharknado (2013) and sequel Sharknado 2: The Second One (2014).
Syfy announced the news at the 2015 Television Critics Association winter press tour Thursday. The first two movies were set in Los Angeles and New York, and the third installment will take place in Washington, D.C. Anthony C. Ferrante will return to direct.
Sharknado 2: The Second One became Syfy's most-watched original television movie, with 3.9 million viewers. The network ordered a third film before the second even premiered, and revealed the sequel would be set on the East Coast in October 2014.
Reid will next appear in Australian horror film Charlie's Farm, and is rumored for romantic comedy Tie the Knot. Ziering recently appeared in drag racing movie Snake & Mongoose, and family feature Christmas in Palm Springs.