8 BULLETIN 33, U. S. DEPAKTMENT OF AGRICULTURE. 



The average wind velocities in miles per hour during the months 

 from May to August for the years 1908 to 1913, inclusive, are pre- 

 sented in Table III. 



Table III. — Average wind velocity at the Dickinson substation, by months, 

 from May to August for the years 1908 to 1913, inclusive. 



[Data (in miles per hour) from the records of the Biophysical Laboratory of the Bureau of Plant Industry.] 



Month. 



190S 



1909 



1910 



1911 



1912 



1913 



Average. 







9.4 

 7.0 

 5.6 

 4.9 



8.0 

 6.7 

 6.1 

 5.4 



9.6 

 7.3 

 7.5 

 6.4 



9.6 

 6.6 

 5.6 

 7.1 



8.1 

 7.9 

 6.4 

 5.5 



8.9 



June 



8.9 

 4.9 

 5.9 



7.4 



July 



6.0 





5.8 









6.6 



6.7 



6.6 



7.7 



7.2 



7.0 



7.0 







Table III shows the average wind velocity at Dickinson to be 7 

 miles per hour from May 1 to August 31. It also shows that there 

 is a general decrease in the velocity of the wind from May to August. 

 The greatest seasonal velocity was recorded in 1911, which was the 

 year of least rainfall and greatest evaporation. During July of that 

 year protracted hot winds occurred, which caused the velocity for 

 that month to be unusually high. The low yields recorded in 1911 

 were due largely to injury to the growing crops by these winds. 

 The wind for any one day (24 hours) very seldom exceeds a total of 

 500 miles, while the hourly velocity seldom exceeds 30 miles an hour. 

 The wind is usually from the northwest or the southeast. 



TEMPERATURE. 



A maximum and minimum thermometer and a dry-bulb ther- 

 mometer are in constant use at the substation during the summer 

 months. A summary of the mean, maximum, and minimum tem- 

 peratures during April to August, inclusive, for the past seven years 

 is presented in Table IV. 



Table IV. — Summary of mean, maximum , and minimum temperatures at the 

 Dickinson substation, by months, for the crop season (April to August) of 

 the years 1907 to 1913, inclusive. 



[Data (in °F.) from the records of the Biophysical Laboratory of the Bureau of Plant Industry.] 



April. 



May. 



June. 



July. 



August. 



Year. 



Seasonal 

 mean. 



1907 35 



1908 43 



1909 34 



1910. 



1911 39 



1912 44 



1913 46 



Average. 



69 



5 

 -6 



4 

 18 



6 

 16 

 19 



22 60 



93 

 97 

 93 

 107 

 101 

 91 



97 



97 

 100 

 94 

 97 

 95 

 87 

 97 



