A UV weatherable film construction is provided which is capable of retaining its dimensional stability under extreme environmental temperatures and humidities. The base film polymer, syndiotactic polystyrene, has characteristically low moisture absorption, excellent thermal stability, and high transparency. When used in combination with a UV-blocking coating, the sPS film exhibits a degree of resistance to UV-induced discoloration and degradation that is substantially superior to unprotected sPS films or films based on sPS resins that are merely compounded with a UV absorber. The sPS cover films of the present invention are useful as overlay films in signing and other outdoor applications, are comparable to UV-absorber loaded acrylic films in UV blocking or resistance, and provide a cost competitive alternative to acrylic, polyester, and fluoropolymer overlay films.