Relay for Life of Polk County is celebrating &uot;25 Years of Hope.&uot; The theme for this year&39;s event is &uot;Hope for a Silver Lining.&uot; The event, which raises funds for the American Cancer Society, will be held Friday, May 29 at 7 pm. at Polk County High School.&bsp; Participants walk the track throughout the night, enjoying music and other entertainment. Food and other activities are also available all through the night. he opening ceremony and survivor lap will take place at 7 p.m., a luminary service in which participants walk the track with candles will be at 9:30 p.m., and the closing ceremony will be at 7 a.m. Many area organizations form teams to participate in Relay for Life, with each team trying to keep at least one team member on the track all night.