TEMPERATURE – Few states have greater temperature extremes than Oregon where they have ranged from a low of 54° F below zero to a high of 119° F. Seldom, however, do daily extremes occur even closely approaching these absolute records. In 80 percent of recent years the highest temperature recorded in the State has not exceeded 114° F, nor was the absolute minimum lower than -37° F. In 50 percent of those years no temperature was recorded higher than 110° mark. Here the mean of the coldest month, January, is 45° F only 15° less than that of July, the warmest month. In the Willamette Valley few stations have had a maximum temperature greater than 98° F, or a minimum temperature lower than 16° F for over half of their years of record. Temperature of 90° F or more, occur only about six to eight days a year and those below zero occur on an average of once every 25 years. Here the mean temperatures average 38° F in January and 66° F in July. In the inland valleys of the southwest the average summer temperatures are about 5° F higher than in the northwest and maximums of 90° F or more occur 40 to 50 days a year. In south-central Oregon the median annual maximum temperatures over a period of years have been between 95° F and 100° F, varying, of course, with the different stations; in most other areas east of the Cascades this variance is between 100° and 105° F. Median annual minimum temperatures for eastern Oregon vary from near zero in the more protected areas of the Columbia Basin to -26° F in the high mountain and plateau regions. The minimum for majority of these stations, however, lies in the range of –1 to -10° F. The normal mean January temperature in southeast Oregon is 25° to 28° F and in the northeast 29° to 33° F; July normal means range between 65° and 70° F in the central valleys and plateau regions and 70° to 78° F along the eastern border.
