LAND AND OTHER AGENTS OF PRODUCTION 135 



thus favoring the growth and maturity of the crops. The years of 

 greatest rainfall are not always the most favorable years for the pro- 

 duction of crops, the harvesting of a successful crop seeming to depend 

 more upon the absence of hot, drying winds and upon the timeliness 

 of the rainfall rather than upon the total amount precipitated. The 

 snowfall varies from but a few inches to several feet. It is, however, 

 generally of a dry character and is readily removed from the exposed 

 prairie surface and slopes by winds, so that while collecting as deep 

 drifts in coulees, railroad cuts, or in other depressions, the grazing of 

 stock upon the exposed hillsides and slopes in the broken lands is 

 usually not greatly interfered with. 



Hailstorms are of relatively frequent occurrence and are often 

 very destructive, and the insurance of crops against damage by hail 

 is a .common practice. Hailstorms are, however, of local character, 

 and while the destruction wrought to crops is often complete, it is 

 confined to relatively narrow strips or to small spots, and but a small 

 proportion of the country is affected during any single season. 



The winter season is long and generally marked by long periods 

 of severe temperature, ranging well below zero, and occasionally 

 reaching 30 to 40 F. Killing frosts may occur early in Septem- 

 ber, the average date of the first killing frost falling about the middle 

 of this month. The last killing frost is generally looked for about the 

 middle to the latter part of May, but light frosts may occur in almost 

 any month of the year. During the summer the days sometimes 

 become extremely warm, 90 to 100 F. or even higher temperatures 

 being occasionally reached ; 114 has been recorded at Medora. Nights 

 are usually cool, a variation of from 50 to 60 between the extreme 

 temperatures of the day and night being sometimes experienced. 



The wind movement is generally brisk and days of relatively high 

 winds are not of infrequent occurrence, particularly during the winter 

 and spring months. Gales of considerable severity often accompany 

 the local thunderstorms of the summer months. Damage is some- 

 times caused by the lodging of grains or the insecuring of farm build- 

 ings occupying exposed places. During the summer months there 

 are brief periods of hot, dry winds, causing excessive evaporation and, 

 when these occur, during periods of drought, sometimes injuring the 

 growing crops. 



The popular belief that a permanent climatic change has taken 

 place and that there will be no further repetition of successive 

 seasons of unusual drought is unfounded. 



