Geography of Washington County, Oregon

North America

Washington County, located in the northwestern part of Oregon, is a diverse and vibrant region known for its fertile farmland, thriving urban centers, and natural beauty. From its lush forests to its scenic rivers and lakes, Washington County offers a unique blend of geographical features and cultural attractions that define its environment and shape its identity.


According to Harvardshoes, Washington County spans approximately 727 square miles (1,884 square kilometers) in northwestern Oregon. It is bordered by several other counties, including Multnomah County to the east, Clackamas County to the southeast, Yamhill County to the southwest, and Columbia County to the north. The county’s landscape is primarily characterized by rolling hills, fertile valleys, and forested areas.

The Tualatin Valley, located in the eastern part of the county, is the largest valley in the region and serves as the heart of Washington County’s agricultural industry. The valley is known for its rich soil, mild climate, and diverse crops, including berries, wine grapes, and nursery plants.


Washington County experiences a Mediterranean climate with mild, wet winters and warm, dry summers. Summers are typically warm and sunny, with average high temperatures in the 70s to 80s°F (21-27°C) and low humidity levels. Occasional heatwaves can occur during the summer months, but temperatures are generally moderated by the proximity to the Pacific Ocean.

Winters in Washington County are mild and rainy, with average high temperatures in the 40s to 50s°F (4-10°C) and frequent precipitation. Snowfall is rare in the valleys but can occur in the higher elevations of the Coast Range and Cascade Range.

Spring and fall are transitional seasons characterized by mild temperatures and fluctuating weather patterns. Spring brings blooming flowers and the return of migratory birds, while fall brings cooler temperatures and colorful foliage.

Rivers and Lakes:

Washington County is traversed by several rivers and streams, providing habitat for fish and wildlife and offering recreational opportunities for residents and visitors alike. Some of the notable rivers and streams in Washington County include:

  1. Tualatin River: The Tualatin River flows through the heart of Washington County, offering opportunities for fishing, kayaking, and wildlife viewing. The river is known for its scenic beauty and diverse aquatic habitat, including trout, bass, and salmon.
  2. Willamette River: The Willamette River forms the eastern boundary of Washington County, separating it from Multnomah County. The river provides opportunities for boating, sailing, and fishing, with scenic views of the surrounding countryside.

In addition to its rivers and streams, Washington County is also home to several lakes and reservoirs, including Hagg Lake and Henry Hagg Lake. These water bodies provide additional recreational opportunities for swimming, boating, and picnicking.

Forests and Natural Areas:

Washington County is home to several forests and natural areas, including the Tualatin Hills Nature Park and the Fernhill Wetlands. These areas provide habitat for a variety of plant and animal species, as well as opportunities for hiking, birdwatching, and nature photography.

The Coast Range, located in the western part of the county, is characterized by its dense forests, rugged terrain, and scenic beauty. The Tillamook State Forest, located just west of Washington County, offers miles of hiking trails, camping areas, and scenic viewpoints.


Agriculture is an important industry in Washington County, with the Tualatin Valley serving as the heart of the county’s agricultural production. The valley’s fertile soil and mild climate support a diverse range of crops, including berries, vegetables, nursery plants, and wine grapes.

The county is also known for its nurseries and greenhouse operations, which produce a variety of ornamental plants, flowers, and shrubs for wholesale and retail markets. Agriculture-related industries, including food processing, packaging, and distribution, play a significant role in the county’s economy.

Communities and Economy:

Washington County is home to several cities and towns, each offering its own unique blend of urban amenities, cultural attractions, and outdoor recreation. The county seat and largest city is Hillsboro, known for its high-tech industry, historic downtown district, and cultural events.

Other communities in Washington County include Beaverton, Tigard, Tualatin, and Forest Grove, each with its own distinct character and sense of community. These towns serve as centers of commerce, education, and culture for residents of the surrounding area.

The economy of Washington County is diverse, with key sectors including high-tech manufacturing, healthcare, education, and agriculture. The county is home to several high-tech companies, including Intel, Nike, and Tektronix, which provide employment opportunities and contribute to the county’s economic growth and prosperity.

Healthcare and education are also major employers in Washington County, with hospitals, medical centers, and colleges providing essential services and employment opportunities for residents. Agriculture-related industries, including food processing, packaging, and distribution, contribute to the county’s overall prosperity and quality of life.


In summary, Washington County, Oregon, is a region of natural beauty, cultural diversity, and economic opportunity. From its fertile valleys and scenic rivers to its vibrant urban centers and thriving agricultural industry, Washington County offers a unique blend of geographical features and cultural attractions that make it a desirable place to live, work, and visit. With its mild climate, diverse economy, and abundance of natural resources, Washington County remains a treasured destination in northwestern Oregon.