The northern part of the Cascade mountain range is what some meteorologists like to call a “convergence zone.” Basically, because the Olympic Mountains block rain and foul weather from passing over its peaks, the unstable air this creates must go somewhere. It flows around the Olympics to the north and to the south, eventually converging at the North Cascades . What this means to you, intrepid visitor, is that this area tends to get dumped on, particularly in the winter.
This is great news for skiers and snow sports enthusiasts, but it can be a travel inconvenience. By November or so the Highway 20 pass is closed until springtime snowmelt, leaving Highway 2 as the only viable pass north of Interstate 90. Even then, things can be tricky over Stevens Pass , so it is imperative that travelers check out snow reports and carry chains at all times.
Also, be sure to plan loads of extra time to get to the Methow Valley , which can take up to six hours of travel depending on pass conditions. And you can forget about traveling the rugged Mountain Loop Highway  during these months, as its interior stretches are impassable once the snow falls.
In the summer, things open up considerably, and the favored route east is definitely the scenic Highway 20. It twists and turns directly through North Cascades National Park , by wild rivers, glacier lakes, and breathtaking passes. However, these mountains are unpredictable, so be sure to bring lots of layers—particularly if you plan on hiking or camping. It is not unusual to see summertime snow. Once you get over the passes, though, it is typically much warmer than the Puget Sound, so don’t forget your shorts when you head to Winthrop , Chelan , and other summer destinations.
Most of these areas are surrounded by Forest Service land. If you plan on enjoying trails and scenic areas, come prepared with a Northwest Forest Pass (800/270-7504, www.fs.fed.us/r6/passespermits/nwfp , $5 per day, $30 annual). This is your golden ticket to recreational fun—it is required at virtually every trailhead and parking spot on Forest Service land here. You can get one online or at any Forest Service office. You can also find them at certain sporting goods store—check the website for details.