Sequim /ˈskwɪm/ is a city in Clallam County, Washington, United States.As of the 2010 census counted a population of 6,606. [Sequim School District population served is a little over 29,000.Sequim and the area around Sequim has a population of about 28,000] Sequim is located along the Dungeness River near the base of the Olympic Mountains.The city has been increasing in population dramatically in recent years due to the influx of retirees from the Puget Sound region and California.equim lies within the rain shadow of the Olympic Mountains and receives on average less than 16 inches (410 mm) of rain per year—about the same as Los Angeles, California—and has given itself the nickname of Sunny Sequim.