Melting snows in the Cascade Mountains turn rivers into raging torrents on both sides of the range. Guided whitewater trips are especially good on the Wenatchee River (perhaps the best in the state) and Methow River, both on the Cascades eastern flank. Peak run-off occurs in late spring and early summer. Book whitewater trips in mountain towns like Winthrop, Leavenworth, and Wenatchee. In the fall, the Wenatchee River loses flow, calming down enough to become a first-class fly-fishing stream. Also on the east slopes of Cascades, the Naches, Stehekin, and Tieton rivers swell with early season whitewater.
On the Cascades western flank, glacier-fed rivers like the Skykomish, Suiattle, and Sauk offer good whitewater conditions well into the summer. Other streams like the Cedar, Green, and White show their best whitewater early in the season. Still others like the Skagit offer excellent scenic float trips (as opposed to whitewater) all through the summer.
In the Olympic Mountains another host of streams flow to the sea, presenting both whitewater rafting (particularly on the Elwha River near Port Angeles) and seasonal float trips by wooden dory to fish for salmon and steelhead. Consider especially the Bogachiel, Clearwater, Hoh, Quillayute, Quinault, Queets, and Sol Duc rivers.
Down in the Columbia Gorge, rivers like the Wind, Washougal, White Salmon, and the Klickitat run big with spring snow-melt. Once again, the best whitewater rafting comes in May and June, with excellent scenic and fishing float tours later in the summer and fall when waters calm down.