CLIMATE 



55 



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

 autumn. 



Station 



Years of 

 Obser- 

 vation 



Glasgow 14 



Chinook 10 



Glendive 16 



Poplar 16 



St. Paul 10 



Adel 10 



Chouteau 11 



Fort Benton 



Lewistown 12 



Crcat Falls 18 



Cut Bank 7 



Billings 1.0 



Crow Agency 27 



Miles City IS 



Red Lodge 8 



Bozeman 8 



Butte 14 



Fort Logan 12 



Helena :5"> 



Dillon 9 



Anaconda 8 



Columbia Falls 16 



Kalispell 12 



Missoula 10 



uvando 10 



Troy .. 13 



L,ast frost 

 in spring 



May 22 



" 13 



" 12 



" 16 



29 



June 25 



May 30 



" 16 



June 5 



May 7 



June 14 



May 7 



" 15 



June 13 

 May 28 

 June 5 



" 16 

 May 7 

 June 9 



" 13 



9 



May 13 



" 13 

 July 4 

 June 1 



First frost 

 in autumn 



Sept. 12 



" 11 



" 22 



" 11 



" 16 



Aug. 24 



Sept. 6 



" 30 



" 3 



" 16 



Aug. 29 



Sept. 16 



" 26 



" 24 



a 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 

 f restless season and some with a difference of 100 miles or over 

 in latitude have a difference of 30-50 days 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. 



