30 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



If the records are considered separately for the stations located 

 within the line of 10 inches of rainfall the average number of clear 

 days for these same years is 166, 168, and 193. 



These data show very clearly that eastern Washington has much 

 more sunshine than western Washington, and also that in the region 

 of less than 10 inches rainfall, Avhich closely coincides with the 

 Upper Sonoran area, the amount of sunshine is considerably greater 

 than for the average of eastern Washington. 



The following percentages are based on the normal sunshine map 

 of the United States Weather Bureau : The least amount of sunshine 

 is in the very humid region, which has over 90 inches of annual rain- 

 fall. Less than 40 per cent of the days here are clear, a low percent- 

 age equaled in the United States only on the upper peninsula of 

 ]\Iichigan, in northern New York, and in northern New England. 



In the region of less than 10 inches rainfall over one-half of the 

 days of the year are clear, thus corresponding in general with the 

 broad basins of the Missouri and Mississippi valleys and with the 

 Southern States. The remainder of the State has from 40 to 50 per 

 cent of the days clear, resembling in this respect the region of the 

 Ohio Valley northward and eastward. 



TEMPERATURE, 

 WESTERN WASHINGTON. 



Temperature records of the United States Weather Bureau are 

 available for over 30 stations in western Washington, all located 

 in the Humid Transition area, for periods varying from one year to 

 thirty years. The nomial annual mean temperature based on these 

 records is 49.3° F. The same average for each of the 30 stations 

 shows the lowest to be Port Crescent, 46.6°, and the highest to be 

 Vancouver, 52°. The normal monthly mean temperatures of the 

 same stations vary as follows : 



Temperature data for Humid Transition area. 



Month. 



January . 

 February 

 March... 



April 



May. 



June 



Degrees F. 



35 to 40 



37 to 43 



38 to 46 

 45 to 51 

 50 to 58 

 54 to 62 



Month. 



July 



August ... 

 September 

 October . . . 

 November 

 December 



Degrees F. 



56 to 66 

 56 to 66 

 53 to 60 

 47 to 53 

 38 to 46 

 34 to 43 



The highest temperature ever recorded at any of these stations is 

 100°: the lowest is— 2°. 



