CHAPTER V 

 CLIMATOLOGY 



The climatic conditions which have the most notable 

 effect upon agricultural production and the limiting of 

 certain crops to special areas are temperature and rainfall. 

 These two factors, and in particular their variation from 

 season to season and year to year, are the subject of much 

 discussion. 



Climatic cycles. In a general way both temperature and 

 rainfall run in cycles. There are periods of cold and warm 

 years and periods of wet and dry. Some of these are of 

 longer duration than others, but no relation exists between 

 their beginning and ending and the length of time throughout 

 which they extend. However, there is a tendency gradually 

 to increase and then decrease, several years elapsing between 

 the extremes. Some authorities have estimated that it 

 requires records covering thirty-five successive years to 

 determine the averages for a given locality. It is doubtful 

 whether this time is long enough to cover the greatest 

 extremes. It would probably require observation for a 

 century to get the maximum range of high and low tem- 

 perature or the greatest and smallest rainfall on a specified 

 area. The statements frequently heard to the effect that 

 winters are growing warmer or the rainfall more plentiful 

 have their foundation only in the cycles referred to. The 

 records of the United States Weather Bureau indicate that 

 there are no general climatological changes, and one may 

 expect winters as cold, summers as hot, and seasons as wet 

 or dry as have ever been experienced in the past. 



Promoters frequently take advantage of a certain condition 

 of season to develop agricultural interest in a locality affected. 

 A few wet years in an arid region bring out the assertion 



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