Eye on MI | Summer Celebration A mile run and community parade kicked off Mercer Island's annual Summer Celebration on Saturday, July 14. By Reporter Staff • July 14, 2012 9:50 pm Kids take a spin in Mercerdale Park during Summer Celebration on Saturday A mile run and community parade kicked off Mercer Island’s annual Summer Celebration on Saturday, July 14. The theme of the weekend is “Spirit of the Olympics.” Temperatures peaked in the mid-70s with the sun coming out after an overcast morning.