THE CLIMATE OF WESTERN CANADA 29 



of the crop in the northern parts of the Prairie Pro- 

 vinces (chiefly Alberta and Saskatchewan) was injured 

 by a heavy frost on the night of July 24th. 



The purpose of instancing these facts is to show that 

 ths "average" time of frost is sometimes widely departed 

 from, both in the favorable and unfavorable directions. 

 This suggests fR05T5 of 5° 



even more forci- 

 bly than the 

 short time be- 

 tween frosts, 

 the desirability 

 of (1) growing 

 "safer" crops, 

 and (2) devel- 

 oping a more di- 

 - versified agri- 

 culture, partic- 

 ularly in the 

 temperature zones showing the greatest variations from 

 the average. 



18. Frost Resistance of Different Crops. — Cereals will 

 withstand heavy spring frosts but not fall frosts. Root 

 crops and rape will withstand heavy fall frosts but 

 suffer considerably from heavy spring frosts. Corn 

 and potatoes will withstand neither, although potatoes 

 will live through frosts that kill corn. Flax and peas 

 suffer considerably from both spring and fall frosts, 

 while perennial grasses and legumes will withstand very 



, low temperatures at either season. 



19. The Average Temperature of the Growing Period. 

 — The average temperatures at representative points for 

 each month in the year are indicated on the diagram, 



Fig. 14. — Frost-Free Period at Different Points. 



Above, length of period between spring and fall 



frosts of three degrees. Below, length of 



period between frosts. Twelve year 



average. 



