PIPER FLORA OP THE STATE OF WASHINGTON, 29 



approached only by that of the regions about Mobile, Ala., and Cape 

 Hatteras, N. C. The rainfall of the Puget Sound Basin as a whole 

 is but slightly in excess of that of the Atlantic coast States, but it 

 shows wide variation within short distances. The greater part of 

 eastern Washington coincides as regards total rainfall with the upper 

 Mississippi Valley. 



A noticeable peculiarity of the Washington rains, particularly in 

 the western part of the State, is their gentleness. They are rarely 

 accompanied either by winds or by lightning. Perhaps 90 per cent 

 of the rains consist of gentle drizzles, locally characterized as " Ore- 

 gon mists." 



A most striking feature of the rainfall is the very low amount of 

 precipitation during the summer months. This has given rise to a 

 distinction between a " dry " or summer season and a " wet " or winter 

 season, though in reality the wet season includes much of the spring 

 in all parts of the State, and also of the fall, particularly in western 

 Washington. 



A prolonged " dry " season naturally entails drought, which may 

 be marked even in the humid western portion of the State. In east- 

 ern Washington such droughts have occasionally caused severe injury 

 to crops. 



The significance of this dry season is rendered more clear by com- 

 parison. If we except the Vancouver strip, all of the United States 

 west of the Rocky Mountains has normally less than 3 inches of rain- 

 fall during July, August, and September, an amount lower for these 

 months than any other part of the country. For eastern Washington, 

 as a whole, the rainfall of these three months averages about 2 inches. 



The normal annual rainfall for the Vancouver strip during the 

 three summer months is less than (5 inches, thus coinciding with that 

 of the area between the one hundredth meridian and the Rocky 

 Mountains. 



SUNSHINE AND CLOUDINESS. 



The average number of clear days in western Washington for the 

 years 1902-1904 was, respectively, 120, 127, and 117; of partly cloudy 

 days, 92, 100, and 80; of cloudy days, 153, 148, and 159. As might be 

 expected in conformity with the wide variation in rainfall, the 

 extremes depart considerably. The smallest numbers of clear days 

 were, respectively, 56, 42, and 48 ; the largest, 171, 174, and 174. 



In eastern Washington for the same years the clear days totaled, 

 respectively, 146, 153, and 178 ; the partly cloudy days, 92, 95, and 90; 

 the cloudy days, 127, 117, and 98. The largest numbers of clear days 

 were 207, 228, and 230. The smallest records for the same years were 

 07, 77, and 85. 



