It is possible to get a taste of Olympic National Park on a day trip from the Seattle area. Depending on where you start and where you are heading, it is a bit over a three hour drive each way. This means a bit of driving, but it also means a lovely visit to Hurricane Ridge, the Dungeness Spit or perhaps some other part of the park. It might be tempting to visit the Pacific Beaches or the Hoh Rain Forest, but this would take mean a lot more time in the car and, even during our long summer days, less time to explore. Use the planner on the Just a day trip page to get a sense of what might fit in a reasonable day on the road.
This would be a great way to spend a weekend. Drive out to the peninsula, explore the park, spend the night, then see more of the park the next day. You could still get back to Seattle in the evening. Do be warned that if you actually try to do this on a summer weekend, you may run into long lines for the ferries, particularly on Friday and Sunday evenings. Otherwise, use the planner on the An overnight in Port Angeles page to get an idea of what you can fit into a day and still have time for driving from and back to Seattle.
If you have more time, you can really get to explore the park. Getting out to the West End on a day when you are driving from or to Seattle can mean a lot of time in the car. Longer trips mean full days for longer excursions. You can spend a whole day at Cape Alava, check out the West End Beaches, or take a long hike at the Hoh Rain Forest and still have a nice dinner and a quiet evening. This site has planning pages for three day and four day visits or use our Longer stays page for a more general approach.