Well, 80% of it one time, the other 20% another time.

The only two problems are:

a) sometimes there really isn’t a highway along parts of the U.S. Pacific coastline for quite a while… I’m specifically talking about Mendicino county in northern California. Hwy 1 curves into 101 in the middle of the Mendicino forest. 101 then curves back out to the ocean just before it hits the Oregon border. From there on north, PCH = 101, pretty much

b) Seattle isn’t on the Pacific coast! It’s actually almost 100 miles inland from the actual Pacific Ocean. It definitely is surrounded by water, and has temperate weather because of it.. however an oceanside city Seattle is not.

If you change “Seattle” to “Neah Bay”, now you’re talkin’!

..although even then, 101 is a strange looping beast in the Olympic peninsula in WA State.. the concept of “101 south” and “101 north” gets extremely twisted. Also, you’ll find yourself going north up on the Long Beach peninsula in SW Washington, and then it dead ends. What the hell! So you have to backtrack all the way, and curve slightly east next time. And then you have all that forest preventing you from seeing the coast much of the time… then you have to curve eastward into Aberdeen… (shudder) ..and, well, it just gets really complex defining “PCH” in Washington state… but the very NW tip of the Olympic peninsula is really pretty, and it’s pretty much as “northwest” as you’ll get in the continental United States. So, to make a short story long, there’s your trip. Enjoy!