PHYSICAL AND CLIMATIC SETTING 25 



ture both in summer and winter and in its smaller 

 rainfall, which is practically negligible, as all crop- 

 ping is conditioned on irrigation. 



The Great Valley differs from the coast regions 

 west of it in having a lower winter temperature, be- 

 cause its dominating environment is the snow-clad 

 Sierra on its east side and the Coast Range on the 

 west. This contrast is more marked through the 

 central and southward stretches of the Great Valley. 

 Another contrast is in summer temperatures which 

 may average more than twenty degrees higher on the 

 east than on the west side of the Coast Range, as the 

 ocean then has a cooling effect on the regions open 

 to its influence. 



In rainfall the Great Valley has such marked dif- 

 ferences that generalization is impossible. Roughly 

 speaking, the Sacramento Valley may be said to have 

 from 20 to 40 inches on different years, while the 

 San Joaquin has from 4 to 16. This variation in 

 rainfall is, however, overcome by irrigation which 

 is practiced in the Great Valley over a greater acre- 

 age than in any other section of the State. The 

 products include all grown anywhere in California. 

 The Great Valley has always produced the chief 

 part of the grain and hay products of the State. Its 

 more recent development has included all of the raisin 

 output and the chief part of the alfalfa, on the basis 

 of which it now leads in dairy industries. It stands 

 first in the production of shipping and canning fruits 

 and in all fruits grown for drying except prunes and 

 on the edges of the valley the citrus fruit product 



