68 OREGON FARMER 



and mild in winter and cool in summer, but is a little more seasonal 

 than on the coast. 



Southern Oregon. 



Irregular offshoots and spurs of the Coast and Cascade Ranges 

 spread out in the southwestern part of the state, forming a more 

 elevated undulating section with somewhat less humid and^more 

 sunny climate. The rainfall averages about 30 inches and runs from 

 35 at Roseburg to 21 at Ashland. About 2 inches falls during the 

 three summer months. There is an average of about 185 days between 

 killing frosts, being similar to that of Central Illinois. The length of 

 season depends on the altitude and the natural air drainage, and 

 ranges from 150 to 200 days. The mean temperature for January 

 is about 40 degrees and for July about 60 degrees. There are 16 

 days in a year when the temperature rises above 90 degrees and 50 

 days when if falls below 32 degrees. The climate is somewhat more 

 seasonal than for the Willamette Valley but it is free from extremes 

 of any kind. The winters here are mild and the summer nights cool. 



Columbia Basin. 



East of the Cascades is the Columbia River Basin, 50 to 75 miles 

 wide and about 150 miles long. It has a mean elevation of about 

 1,000 feet and a general northernly dip towards the river. Here the 

 climate is dry and sunny. The relative humidity is low and evapora- 

 tion from a water surface is high. The annual rainfall for the district 

 averages some 14 inches ranging from about 10 inches near the river on 

 the Umatilla irrigation pro j ect to 24 inches at Weston. Rainfall increases 

 with altitude and distance from the river. While the heaviest rains 

 are in winter there is a secondary maximum in May and June. 

 In the foothill districts these early summer rains come as torrential 

 showers. The mean annual temperature near the river reaches 56 

 degrees, the highest for the state. It decreases with altitude to 47 

 degrees in the foothills of the Blue Mountains. There is a very long 

 growing season along the Columbia, averaging about 200 days. The 

 average for the district is about 157 days, corresponding to that of 

 southern Wisconsin. Strong breezes are common along the river but 

 decrease upon going back from the river and to higher altitudes. The 

 nights are cool, the days clear and the air fresh and invigorating. 

 Blue Mountain District. 



In Northeastern Oregon is situated the high irregular range of the 

 Blue Mountains, between the various groups of which very productive 

 elevated valleys are situated. These and the other scattering 

 mountains of Eastern Oregon cause precipitation of the limited supply 

 of moisture which escapes the Coast and Cascade Ranges. The 

 rainfall ranges from 12 to 23 inches and averages about 16 inches 

 annually The growing season ranges from 100 to 150 days, averaging 

 about 140 days in the valleys and decreasing with the altitude. There 

 are many sheltered valleys where the season permits commercial 

 fruit growing. The mean summer temperature corresponds to 

 central Wisconsin and that of winter is similar to northern Iowa. 



