CLIMATE AND VEGETATION 



Temperatures in the county are usually mild. Summer is char- 

 acterized by warm days and cool nights. Rainfall is primarily a 

 winter phenomenon; during the drier summer months it is usually a 

 product of local electrical storms. Summer days are usually cloudless 

 and humidity is very low; less than 10% is not uncommon in the 

 valleys and mountains. Most winter days are heavily overcast and fog 

 is common in the Lower Rogue River Valley during most of December. 



Climatic data are presented in Table 1. Data from Crater Lake 

 National Park in Klamath County are included as representative of 

 the southern Cascade Mountains in Oregon. 



Precipitation in Jackson County varies in form and amount. The 

 driest months at Medford are July, August, and September. Most of 

 the rainfall (28 cm) at Medford occurs from November to February; 

 December, the wettest month, has an average of 8.9 cm (Rudd 1962). 

 The distribution of precipitation in the mountains of Jackson County 

 is similar to that in Medford but is mostly in the form of snow. 



The vegetation of Jackson County is best described in terms of 

 forest coverage. Earlier concepts of vegetation distribution (see Bailey 

 1936) in the county recognized five life zones — Upper Sonoran, Transi- 

 tion, Canadian, Hudsonian, and Arctic-Alpine. Peck (1941) described 

 nine vegetation areas for Oregon using a system that more closely 

 approaches the plant community concept and allows a more ecological 

 interpretation of a geographic area. A classification of plant com- 

 munities adapted from Munz and Keck (1959) is used here to describe 

 the vegetation of Jackson County (Fig. 1). The system adapted is 



Table 1. Climatic data from re-presentative weather stations in Jackson County, Oreg. 



station 



Aver- 

 age 

 annual 



Temperature (F) 



Aver- 



Janu- 

 ary 



Aver- 

 age 

 mini- 

 mum 

 Janu- 

 ary 



Aver- 

 age 

 July 



Aver- 

 age 

 maxi- 

 mum 

 July 



Precipitation 

 (inches) 



Aver- 

 age 

 annual 



Aver- 



Frost 

 free 

 days 



Medford 54 37 30 72 89 20 7 161 



Prospect 50 35 26 66 88 42 64 



Siskiyou Station 48 34 26 65 76 33 



Crater Lake 1 39 25 18 54 6'6 70 589 71 



1 Conditions for southern Cascades in Jackson County less extreme. 

 Source: U.S. Weather Bureau 1965, Rudd 1962, Farner 1952. 



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