CLIMATE 



55 



Table 7. Average dates of last killing frost in spring and first in 

 autumn. 



Station 



Years of 

 Obser- 

 vation 



Ijast frost 

 in spring 



First frost 

 in autumn 



Glasgow 



Chinook 



Glendive 



Poplar 



.St. Paul 



Adel 



Chouteau 



Port Benton 



Lewistowu 



Great Falls 



Cut Bank 



Billings 



Crow Agency ... 



Miles City 



Red Lodge 



Bozeman 



Butte 



Fort Logan 



Helena 



Dillon 



Anaconda 



Columbia Falls 



Kalispell 



Missoula 



Ovando 



Troy 



14 

 10 

 16 

 16 

 10 

 10 

 11 



9 

 12 

 18 



7 

 10 

 27 

 IS 



s 

 s 



14 

 12 

 35 

 9 

 8 

 16 

 12 

 10 

 10 

 13 



May 22 



" 13 



" 12 



" 16 



" 29 



June 25 



May 30 



" 16 



June 5 



May 7 



Jinie 14 



Mav 7 



15 



7 



June 13 



May 28 



June 5 



" 16 



May 7 



June 9 



" 13 



9 



May 13 



'■ 13 



July 4 



June 1 



Sept. 12 



" 11 



" 22 



" 11 



" 16 



Aug. 24 



Sept. 6 



" 30 



3 



" 16 



Aug. 29 



Sept. 16 



" 26 



" 24 



" 2 



7 



" 15 



Aug. 30 



Sept. 28 



1 



4 



Aug. 22 



Sept. 30 



" 19 



Aug. 12 



Sept. 7 



of stations within the State. In these as in most temperature 

 records, other elements are to be considered besides latitude and 

 altitude. Some stations much higher than others have a longer 

 frostless season and some with a difference of 100 miles or over 

 in latitude have a difference of 30-50 day.s in the frostless period 

 in favor of the more northerly stations without compensating 

 difference in altitude. The proximity of mountain ranges, the 

 width and direction of valleys, the exposure of the slope, and 

 the direction and velocity of winds, all have their influence on 

 the temperature at any time of the year. Owing to the charac- 

 ter of the topography and the extent of the area involved, the 

 figures on temperature can have only the most general sig- 

 nificance. Figure 11 gives, the mean annual isotherms of 1911, 

 one of the colder years, and indicates the complexity of the 

 temperature problem as far as distribution of species is con- 

 cerned. "When local areas are under consideration their tem- 

 peratures must be a subject of local investigation. 



