Sequim (i/skwɪm/) is a city in Clallam County, Washington, United States. The 2010 US Census counted a population of 6,606 residing within the city limits. Approximately 20,000 additional residents live in the Dungeness Valley immediately surrounding the city. 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.
Sequim lies within the rainshadow of the Olympic Mountains and receives an average of less than 15 inches (380 mm) of rain per year—about the same at Los Angeles, California. Yet the city is fairly close to some of the wettest temperate rainforests of the contiguous United States. This climate anomaly is sometimes called the blue hole of Sequim. Fogs and cool breezes from the Juan de Fuca Strait make Sequim's environment more humid than would be expected from the low average annual precipitation. Some places have surprisingly luxuriant forests dominated by Douglas-fir and western red cedar. Black cottonwood, red alder, bigleaf maple, Pacific madrone, lodgepole pine and Garry oak can also be large. Historically, much of the area was an open oak-studded prairie supported by somewhat excessively drained gravelly sandy loam soil, though agriculture and development of the Dungeness valley have changed this ecosystem. Most soils under Sequim have been placed in a series which is named after the city. This "Sequim series" is one of the few Mollisols in western Washington and its high base saturation, a characteristic of the Mollisol order, is attributed to the minimal leaching of bases caused by low annual rainfall.
The city and the surrounding area are particularly known for the commercial growth of lavender, supported by the unique climate: it makes Sequim the "Lavender Capital of North America", rivaled only in France. The area is also known for its Dungeness crab.