The short answer is yes. But, it isn't absolutely necessary for your furniture to discolor and it often takes years for that to happen anyway. Unless your outdoor furniture is in a partly indoor space, it will likely get exposed to direct and indirect sunlight throughout the day. It helps to keep it on a covered patio or under a large umbrella to prevent it from getting too hot. If you aren't using your outdoor furniture for an extended period of time, it is a good idea to keep it in a garage or shed for added protection.