INTERIOR CLIMATES OF CALIFORNIA }5 



VALLEY CLIMATE 



The characteristics of the interior valley climate are higher 

 summer and lower winter temperatures than on the coast, the range 

 of temperature being nearly the same both north and south ; rain- 

 fall abundant in the north and decreasing rapidly southward, so that 

 as a rule the interior valleys in the south half of the State require 

 irrigation ; very dry air and almost constant sunshine, freedom from 

 fogs and from dew in summertime ; winds occasionally strong, hot, 

 and desiccating in summer and cold in winter. 



Local Modifications. The term "valley climate" is broad, and 

 includes everything away from the coast to a certain elevation on 

 the slope of the mountains. Certain small valleys protected from 

 cold northerly winds and from fog-bearing westerly winds and open 

 to the spring sunshine, have a forcing climate which produces the 

 earliest maturing fruit of the season ; earlier not only than the coast 

 and the mountain, as has been stated, but also somewhat earlier than 

 adjacent locations in the broad, open valley. Slight elevation, even 

 on the sides of small valleys, frequently secures freedom from winter 

 frosts and ministers to early ripening. Elevation above sea-level on 

 the rims of great valleys also secures similar results and gives rise 

 to thermal belts in which semi-tropical fruits are successfully grow- 

 ing even as far north as Shasta County. On the floors of great 

 valleys moderating influences are secured on the lee side of wide 

 rivers and by planting on the river bank or on slightly elevated 

 swells rather than on the level, open plain. The river bottom lands 

 of the great valleys, though subject to severe frosts, are freer from 

 the effects of desiccating winds than the open plains ; they are, how- 

 ever, more favorable to the spread of certain blights than the plains. 



Some of the horticultural effects of valley conditions are as fol- 

 lows : Early ripening and perfection of summer and autumn fruits, 

 owing to continual sunshine and dry air ; forced maturity of certain 

 fruits, as apples for instance, which destroys character and keeping 

 quality ; injury from sunburn and hot winds in summer, which seri- 

 ously affect both fruit and foliage of some varieties ; occasional 

 injury to tender fruits (semi-tropicals) and to young trees of hardy 

 fruits, which have been kept growing late in the season, from low 

 temperature, which sometimes is reached suddenly on the floor of 

 the valleys ; freedom from some blights and insects which are pre- 

 valent on the coast, but not from others. Many of these minor 

 troubles are, however, counterbalanced by the earliness, size, beauty, 

 and quality of certain fruits, and by the most rapid and successful 

 open-air drying of fruits, owing to high autumn temperature, the 

 freedom from summer fog, dew and generally from rain during the 

 drying season. 



FOOTHILL CLIMATE 



Foothill climate is usulaly considered as a modification of valley 

 climate. It has been shown that up to about two thousand five 

 hundred feet, on the western slope of the Sierra Nevada, the seasonal 



