4 BULLETIN 219, U. S. DEPARTMENT OF AGRICULTURE. 



The altitudes vary from approximately 1,400 feet in the north 

 to 6,000 feet at Cheyenne, Wyo. The southern portion of the terri- 

 tory has a higher average altitude, a higher average rainfall, and a 

 correspondingly higher rate of evaporation than the northern portion. 



CLIMATIC CONDITIONS. 



The climate of the Great Plains has been classified as semiarid. 

 It may be better to say that it is changeable, varying from season 

 to season from almost humid conditions to almost arid, with a mean 

 annual precipitation relatively low. Years of relatively high pre- 

 cipitation may be followed by years of relatively low precipitation. 

 Other climatic factors usually correspond with the rainfall. A 

 year of relatively high rainfall will have a lower rate of evaporation, 

 higher humidity, and lower wind velocity than will be found in the 

 unfavorable years. 



Another climatic factor of much importance in crop production 

 in the G^eat Plains is the distribution of the rainfall. A relatively 

 low rainfall, properly distributed, may produce a crop where a 

 much higher rainfall, coming with unfavorable distribution, may 

 result in a crop failure. 



No attempt will be made in this bulletin to give a full description 

 or record of the climatic conditions at the various stations during 

 the time covered by these investigations. 



Table I gives the maximum, minimum, and average annual and 

 seasonal precipitation and seasonal evaporation at each station for 

 the years for which experimental work is here reported. By seasonal 

 is meant the period between the average time of seeding and the 

 average time of harvesting. 



Table I. — Annual and seasonal precipitation and seasonal evaporation at fourteen 

 stations in the Great Plains area. 1 





Alti- 

 tude 

 (feet). 2 



Precipitation (inches). 3 



Seasonal evapc 

 (inches). 



ration 



Station. 



Annual. 



Seasonal. 



3 





Mini- 

 mum. 



Maxi- 

 mum. 



Aver- 

 age. 



Mini- 

 mum. 



Maxi- 

 mum. 



Aver- 

 age. 



Mini- 

 mum. 



Maxi- 

 mum. 



Aver- 

 age. 



Judith Basin 



Huntley 



4,228 

 3,000 

 1,875 

 2,543 

 1,468 

 2,253 

 2,950 

 3,950 

 3,000 

 4,600 

 2,050 

 2,900 

 4,000 

 3,676 



14.96 

 11.92 

 10.28 

 11.93 

 11.94 

 12.72 

 6.64 

 13.77 

 11.18 

 14.51 

 15.59 

 11.82 

 13.69 

 10.69 



23.78 

 11.92 

 18.99 

 21.22 

 21.95 

 15.68 

 17.73 

 18.51 

 23.01 

 22.46 

 27.80 

 23. 5S 

 16.35 

 27.80 



18.06 

 11.92 

 14.84 

 16.69 

 16.71 

 14.20 

 13.11 

 16.14 

 18.05 

 18.28 

 21.30 

 18.54 

 15.11 

 IS. 28 



7.04 

 5.92 

 4.75 

 6.85 

 7.85 

 8.92 

 4.08 

 2.53 

 6.85 

 6.42 

 8.18 

 2.79 

 5.09 

 6.17 



17.21 

 6.02 

 14.49 

 16.28 

 14.98 

 12.47 

 9.78 

 8.52 

 12.66 

 13.86 

 17.97 

 14.43 

 9.85 

 11.38 



9.34 

 5.97 

 9.66 

 9.79 

 10.11 

 10.36 

 6.90 

 4.69 

 9.45 

 9.02 

 11.17 

 8.65 

 8.01 

 9.13 



22. 012 

 23. 754 

 20. 422 

 20. 673 

 18. 663 

 21. 539 

 26. 472 

 23. 804 

 28. 445 

 26. 064 

 30. 625 

 34. 325 

 35. 459 

 33. 804 



29. 353 

 24. 214 

 26. 877 

 25. 745 

 24. 893 

 28. 239 

 33. 750 

 29. 381 

 38. 168 

 35. 654 

 44.373 

 43.510 

 41.748 

 42. 076 



24. 491 

 23.984 





24. 216 





23. 919 





21.866 





24. 639 



Belle Fourche 



Scottsblufl 



28. 794 



26. 081 



North Platte 



32. 359 

 31. 420 





35.790 





38.185 

 38.988 





36. 724 







1 The years covered are the same as for the data shown in the other tables for the several stations. 



2 The altitude given is for the field where the work was done and is based in most cases on that of the 

 nearest town. 



3 The records of annual precipitation for 1914 are not included. The records of seasonal precipitation 

 and evaporation for 1914 are included for all stations, being figured from May 1 to Sept. 1. Evap- 

 oration measurements are made from a free water surface, in a tank sunk into the soil to almost its full 

 depth. The water surface is kept about level with the surface of the ground, 



