Joaquin Valley has less than 10 inches (25 cm). The southeastern 

 deserts receive an average of less than 5 inches (13 cm) per year, 

 and in a few areas, such as Death Valley, some years may pass by 

 without any measurable rainfall. The extremes in average annual 

 rainfall range from an excess of 1 10 inches (280 cm) in parts of 

 Del Norte and Siskiyou Counties to less than 2 inches (5 cm) per 

 year at Furnace Creek Ranch in Death Valley. 



Most of the rainfall that occurs in California falls during the 

 winter months. The rainy season in southern California is gener- 

 ally during a period of five months between November and March; 

 in northern California it is during a seven-month period between 

 October and April. There are as many as 100 days of measurable 

 rain on the average in parts of northern CaHfornia; there are as 

 few as 10 days in some desert regions. In the calendar year 1909, 

 over 153 inches (389 cm) of rainfall were recorded at Monumental 

 in Del Norte County; during one season (July 1 — June 30) over 

 160 inches (406 cm) of rain were recorded at one station in 

 Monterey County. In southern California, there are frequent in- 

 tense seasonal storms during which very heavy amounts of rain 

 fall. For example, one storm in Los Angeles County in late 

 January, 1943, dropped nearly 26 inches (66 cm) of rain in 24 

 hours. On another occasion, over 1 1 inches (28 cm) of rain were 

 recorded in 80 minutes at Campo, San Diego County. Obviously, 

 such heavy amounts of rain during very short periods are of little 

 value to plants and may result in damaging floods in lowland areas. 



Although the average rainfall for much of the state is so low 

 that one might expect few plants to survive such conditions 

 (because it falls mostly during the winter months), many arid 

 areas provide shows of spectacular annuals which flower in early 

 spring. Such displays are conspicuous in the southern end of the 

 San Joaquin Valley and also in portions of the Mojave and Colo- 

 rado deserts. The average rainfall figures for a particular area may 

 not be very helpful in estimating what sort of a vegetation is 

 present in the region, however, because of the yearly fluctuations 

 in rainfall and because of the seasonal distribution of the rain. 

 Prolonged periods of drought may have a negative effect on the 

 survival of woody plants, with the result that shrubs or trees are 

 absent from areas where one might expect them to be present. 



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