Washington and Rainy Passes are located in the
marine west coast climate zone of western
North America. Most
weather fronts originate in the
Pacific Ocean, and travel northeast toward the
Cascade Mountains. As fronts approach the
North Cascades, they are forced upward by the peaks of the Cascade Range (
Orographic lift), causing them to drop their moisture in the form of
rain or
snowfall onto the Cascades. As a result, the west side of the North Cascades experiences high precipitation, especially during the winter months in the form of snowfall. Because of
maritime influence, snow tends to be wet and heavy, resulting in high
avalanche danger. ==References==