494 



STATE BOARD OF AGRICULTURE. 



TABLE 5 DATA SHOWING THE ELEVATION^ LENGTH OF RECORD_, TEMPERATURE 



AND PRECIPITATION AT WEATHER BUREAU ^ATIONS_, UPPER PENINSULA, 



tAverage. 



•May, June, July and August. 



FROSTS. 



Charts V, VI, and VII show, respectively, the average dates of the 

 last killing frost in the spring, the first in autumn and the length of 

 the growing season in various sections of the Upper Peninsula. These 

 are probably the principal limiting factors, as far as the climate is con- 

 cerned, in crop production in northern Michigan. 



The lakes, however, prevent late frost in spring and early frost in 

 autumn, along a narrow strip of shore line and thereby increase the 

 length of the growing season in this limited area by 50 to GO days, as 

 shown in Chart IX. The time of late spring and early autumn frosts 

 along the lake shores compares favorably with sections in central- 

 southern Michigan and the length of the growing season in the two sec- 

 tions is about equal. In some of the more remote interior districts of 

 the Upper Peninsula, however, frosts occur in nearly every month of 

 the year. 



In practically all portions of the eastern half of this region the 

 growing season averages more than 100 days while it is but 80 to 100 

 days in length, on the average, in all interior, western counties. The 

 length of the growing season decreases rapidly from 147 days at Mar- 

 quette, on the lake shore, to 79 days at Humboldt, about 35 miles away 

 and 800 feet higher in elevation. 



