OREGON FARMER 65 



THE CLIMATE OF OREGON. 



BY W. L. POWERS, 

 Assistant Professor of Irrigation and drainage. 



'MONG the factors influencing the agriculture and healthfulness 

 of a state none is more important than climate. The determining 

 factors of a climate in Oregon are chiefly the altitude, nearness to 



the ocean, prevailing winds, and movements of general storm areas. 



The wide variations of these conditions in Oregon cause a great 



diversity of climate and makes possible the production of practically 



everything grown outside the tropics. 



General Topographic and Climatic Conditions. 



The chief topographic features of the state are portrayed by the 

 accompanying rainfall chart of the Weather Bureau, page 64, and 

 the topographic map, which we are permitted to reproduce 

 thru the courtesy of our District Forecaster, E. A. Beals, of Portland 

 (Enclosed). The natural drainage for most parts of the state is 

 northerly into the Columbia or else westward into the ocean. The 

 lofty snowcapped Cascade Range, 5,000 to 10,000 feet in elevation 

 divides the state north and south and serves as a natural barrier in 

 winter between the warm air of the western valleys and the cool air 

 of the plateaus to the east. East of this range the climate is con- 

 tinental in character and is semi-arid with large daily range of tem- 

 perature, cool nights and a preponderance of clear days. The climate 

 of Western Oregon is characterized by its mild moist winter season 

 and bright mild summers with a remarkably long growing season. 

 The Cascade and Coast Ranges cause heavy precipitation in winter 

 from the moist winds and storm areas which blow prevailingly from 

 the southwest off of the ocean. 



The mean annual rainfall from stations of the United States 

 Weather Bureau with records over 10 years in length is shown on the 

 topographic map. In general the rainfall decreases from northwest 

 to southeast across the state and increases on the windward slopes 

 of all mountains. The range is from 132 inches at Glenora on the 

 coast mountains in the northwest part of the state to 10 inches at 

 Vale in Malheur, the southeastern county. The mean rainfall of the 

 valleys in Western Oregon is similar to that of New York; while 

 that of Eastern Oregon is about the same as Denver and Boise. 



The main distinguishing feature of the temperature of the state is 

 the cool nights of summer which insures complete rest after hard 

 labor. The mean temperature varies with altitude and distance 

 inland. In the agricultural valleys in Western Oregon and below 

 2,000 feet elevation the mean temperature is about 52 degrees, which 

 is the same as at Bloomington, 111., and Columbus, Ohio. The mean 

 temperature of Eastern Oregon ranges from 56 degrees along the 

 Columbia to 44 degrees in Southeastern Oregon. 



Most parts of the state are free from high winds. The absolute max- 

 imum velocity recorded is 55 miles per hour. The heavy winter 

 rainfall of western sections of the state is well distributed, the greater 



