Chinook

the name of an Indian tribe which formerly lived near the mouth of the Columbia River. The term has been transferred to a warm, southwest wind which blew from the Chinook country to the region occupied by the Hudson Bay Fur Company at Astoria, Oregon. In Washington and Oregon a chinook is a southwest coast wind laden with the warmth and moisture of the Pacific Ocean. East of the Cascades and east of the Rocky Mountains a chinook is a warm, dry, westerly or northerly wind, coming down the east slopes of the mountains. It is dry because it has precipitated its moisture on the mountain tops, and it is warm because the air is crowded together, or condensed, in descending the mountain slopes. The warmth is due to the operation of a physical law, that compression, or shrinkage of bulk, warms any substance. A chinook is likely to set in at any hour of the day, and to continue from a few hours to several days. A continued chinook flows out several hundred miles from the mountain range. The chinooks modify the winters of eastern Oregon and Washington and of Montana, Idaho, and Wyoming, the western parts of the Dakotas, and the northwestern provinces of British America. Occasionally a chinook, known as a winter thaw, reaches the Mississippi Valley, and something of the sort is noticeable on the eastern slopes of the Alleghenies. Similar winds are known in Switzerland. The chinooks are of great value to stockmen, who depend on standing grass for their cattle during the winter. Oftentimes a heavy fall of snow, followed by cold weather, renders it impossible for the cattle to get at the dried grass. When a warm, dry wind comes speeding down from the distant mountains, the snow and ice disappear in a marvelously short time, and the cattle are out on the plains and hill-sides, feeding abundantly, all danger of starvation happily averted.

The cattle seem to anticipate the coming of a chinook. In times of cold and hunger they may be seen standing knee-deep in the snow with their heads turned toward the mountains, anxiously awaiting the arrival of relief. Near the mountains a chinook may be a heavy gale, but farther out on the plains, it subsides into gentle, light, delightfully warm puffs. The following graphic account shows the effect of a severe snowstorm on grazing cattle in Montana:

The effect on grazing cattle in Montana was especially severe. Thousands of the helpless beasts wandered aimlessly over the hills searching in vain for food and shelter. As the days went by and no relief was afforded, their safety was a question of great moment. No food was obtainable, for the grasses upon which they were wont to subsist lay buried under thirty inches of snow. On the evening of December 1, 1896, the temperature at Kipp, Montana, was--13 deg. F. The air was scarcely moving and the sky was clear. Suddenly over the edge of the mountains in the southwest appeared a great bank of black clouds, their outer edges blown into tatters by the wind. In a few minutes a short puff of hot, dry air had reached the plains and in the following seven minutes the temperature had risen to 34 deg. F. The wind increased in velocity to twenty five miles an hour and the temperature rose to 38 deg. F. Within twelve hours every vestige of the thirty inches of snow had disappeared, leaving the hills bare and the plains covered with water.

A rise of 20 deg. F. in ten minutes is not unusual.