Why is it that Mt. Rainier National Park Possesses the extremely pleasing combination of a vast glacial system, abundant flora and magnificent forests? The most significant reason is found in the climatic factors involved.

The climate of the Pacific Northwest is mild and equable with an abundance of precipitation which comes for the most part during the winter months. Similar latitudes of the interior suffer arctic cold in mild winter and torrid heat in the summer - a climate of extremes. In the Puget Sound region the prevailing winds are from the southwest and west and, coming as they do from the Pacific, the northwest summers are cool and the winters mild.

In addition to its influence on temperature the ocean likewise modifies other elements of climate - precipitation, cloudiness and humidity. Since in the summer the land is relatively warmer than the ocean, the moist air is warmed in passing over the land and there is very little rain - with increase of temperature air has greater capacity for moisture and will not precipitate it as rain. In the winter however, the opposite is the case. The land becomes quite cold and the winds passing over it are chilled, their capacity to carry moisture is lessened and the excess is dropped in the form of rain at the lower elevations or snow in the mountains.

With these generalizations in mind, let us now consider the relation of these factors of climate to some of the great natural phenomena of Mt. Rainier National Park. It will be shown that there is a direct dependance upon climate of nearly all the works of nature which awe visitors to this region.

As one enters the park he is immediately impressed by the grandeur of the trees and the profusion of vegetation of the forest floor. Although little rain is usual in the summer, the constant precipitation during the winter months so thoroughly saturates the soil that long periods of drought in the summer are inadequate to dry up the shade-protected forest floor and arrest the growth of the trees.

The glacial system of Mt. Rainier is directly dependant upon precipitation in the form of snow for its maintenance. Glacial ice, originally new fallen snow, has undergone gradual transformation. When snow falls upon the higher slopes of Mt. Rainier the colder upper atmosphere inhibits and the snows of winter are only partially removed in summer. In this manner the residual snow of each succeeding winter is built up and compacted until pressure and gravity force it to lower elevations. So, since glaciers are directly dependant upon snowfall, it is only natural that glaciers will be largest where the snowfall is greatest and, at the same time, where melting is at the minimum. Such a locality is between the five and ten thousand foot elevations. Here the comparatively warmer winds from the Pacific are chilled by passing over the Cascades and, coming in contact with the cold slopes of Mt. Rainier, their capacity to carry moisture is diminished and the excess of it falls as snow. At Paradise and Yakima Park (Sunrise) the snows usually start as flurries in September and begin to fall in earnest in October, gradually increasing monthly until February when the maximum is reached. In succeeding months there is a gradual diminishing snowfall. July and August are the only months when snow fails to accumulate and even then snowfall is not unknown. Because of the lack of data it is impossible to state at what point the snowfall is greatest; it seems quite certain, however, that above the 10,000 foot elevation the amount diminishes because of the protection of the upper part of the mountain above the average clouds and also because of the prevailing high winds which prevent the snow from accumulating upon exposed ridges.

Although not generally obvious, there is nevertheless a direct relationship between the heavy snowfall of the alpine meadows and the fields of wild flowers. Contrary to popular opinion these plants, in general, are not particularly hardy; they are on the other hand rather frail and are absolutely dependant upon the thick blanket of snow for protection from the cold winter air. The ground which supports this growth is rarely frozen and, as the snow precedes freezing weather, the snow acts as an insulator. Thus, these plants are adequately protected until after the warm days of summer have arrived. The melting snow saturates the ground with moisture and, as soon as the warming rays of the newly exposed earth:

"Each clod feels the stir of might,
An instinct within it that reaches and towers
And, groping blindly above it for light
Climbs to a soul of grass and flowers"

(Lowell)

Thus, many of the natural features of Mt. Rainier National Park are related not only to the mighty volcanic peak resting upon the shoulders of the rugged Cascades, but are the result of a large number of complex factors of which its singular climatic conditions are of significant importance.

Walter M. Chappell
Ranger-Naturalist
Summer 1933