ABB-pattern reduplication (X+丝丝) softens an adjective and often takes 的 at the end. Other common examples: 暖洋洋的 (warm), 香喷喷的 (fragrant), 凉飕飕的 (cool and breezy).
memory
丝丝 literally means 'thread by thread' - the cold seeps in like fine threads, never overwhelming, just sneaking through.
