THANKS TO A fellow named Earl, there are 519 glaciers between Snoqualmie Pass and the Canadian Border, the rainfall tops 100 inches a year, and the snow was so deep back in 1892 that Guy Waring's horses ate each other's tails.

Earl, in the gospel of the National Outdoor Leadership School, is the god of weather. Weather figures as prominently as terrain in the North Cascades. In times of frustation, it helps to have someone to curse. Even in the Pasayten, which lies in the rainshadow of the bigger mountains to the west, the peace is often shattered by oaths shouted up at Earl.

On June 25, for instance, the students of a NOLS wilderness expedition got eight inches of snow.

"na*% Earl!"

Later, learning the fate of the NOLS mountaineering course that got rained on almost every day during the same month, they considered themselves lucky.

The Cascades lie in a volatile part of the world. The weather seems to change every 10 minutes. There are 57 varieties of rain, from the cloud that envelops camp in mist to the sluicing downpour that washes camp away. Hail raps the face while the sun shines. The light ranges from the gloom of leaden overcast to the snowblinding brilliance that once forced a mine caretaker to hike out by feeling his way along wagon ruts. There is the fury of the williwaws, sudden fierce cold winds that scour the mountain passes, and the peace of a sunset when a pale lilac wash lingers in the west past 10 o'clock.

A long trip in the wilderness means living intimately with Earl, and preparing for his caprices with the right equipment. NOLS instructors in the Cascades consider cotton clothes positively hazardous because they are useless when wet. Students are given a checklist with 92 pieces of equipment on it, and a good part of it is wool, or manmade fibers like polypropylene and Fiberpile, a polyester and acrylic blend that retains only four percent water when wet. Sleeping bags are thick slabs of Holofil fiber, for a goose down bag, after the inevitable rain storm, has all the loft of a cantaloupe rind.

Exposed constantly to Earl, the body is swift to adapt. Swollen hands feel normal. Scrapes don't sting as much. The skin seems to reach an equilibrium with dirt. Air cold enough to put slush in a water bottle feels as comfortable as "room temperature."

It is harder, however, to adapt to the sense of exposure that plays on the mind. This is not the fear that floods in while you dangle over the void on a rappel rope, trying not to mark the spot you suspect rescue workers will find your corpse. It is subtler, a mood almost, a feeling of exposure that invades the the mind when you realize how thin the margin is that keeps you alive. No shelter can protect you from nature forever. You huddle in a tent, but do not feel far enough from the elements to be soothed by a sense of sanctuary.