The Pacific Type. 49 



Idaho, Oregon, California, Nevada and western Utah ; in other 

 Avords, the great interior basin and the entire Pacific water-shed 

 from British Columbia to Lower California, excluding the section 

 draining into the giilf of California. The chai'acteristic features 

 are very heavy precipitation during midwinter, and an almost 

 total absence of rain during the late summer. 



The infrequency of summer rain is marked in British Columbia, 

 and thence southward it becom:es steadily more pronounced, 

 passing through the gradations of a single rainless month in 

 northern California, then two and three to its culmination of 

 four rainless months in a considerable part of southern California 

 and western Nevada. There is a tendency in the uj^per half of 

 the San .Joaquin valley and thence southward into the western 

 part of San Diego county for rain to cease about a month earlier 

 and to remain absent a month later than over the rest of the 

 Pacific coast region, the dry season being fi-om .June to Seiotem- 

 ber, inclusive, and being usually unbroken even by a passing 

 shower. 



Eastern Nevada appears to share freedom from rain during 

 July, but the autumnal rains appear in September or earlier, 

 under the influence in the southern part of that state of the 

 Mexican type projecting northward. The marked tendency of 

 the winter rains to continue into spring is evident in Washington, 

 whence it shades with diminishing persistency to northern Cali- 

 fornia and northwestern Nevada. 



It may be remarked that in the Pacific coast regions the 

 amounts of rain vary very greatly, according to the topography of 

 the section and the distance from the ocean ; so that the interior 

 depressions, such as the Sacramento, San .Joaquin and other val- 

 leys, particularly those parallel with the coast, have a scantier 

 rainfall than either the coast itself or the Sierra Nevada and 

 other mountain ranges to the eastward. 



These variations in the total rainfall do not, however, affect 

 the distribution throughout the year, which is typically Pacific 

 throughout the whole region. 



As might be expected where the rainfall is very small, a single 

 month of excessive precipitation occasionally increases the rain- 

 fall so as to be misleading. For instance, it is apparent from 

 inspection that the greatest normal precipitation is that of De- 

 cember at both San Diego, California, and Halleck, Nevada ; yet 

 excessive rainfalls of 9.05 inches in February, 1884, at the former 



