6 
BULLETIN" 883, L T . S. DEPARTMENT OF AGRICULTURE. 
Precipitation summary. Inches 
Mean annual 17. 41 
Mean seasonal (April to July , inclusive) 9. 91 
Mean seasonal (April to August, inclusive) 11. 91 
Greatest seasonal (April to July, 1915, inclusive) 18. 89 
Greatest seasonal (April to August, 1915, inclusive) 19. 52 
Lowest seasonal (April to July, 1900, inclusive) 5. 30 
Lowest seasonal (April to August, 1894, inclusive) 6. 65 
Greatest annual (in 1876) 30. 92 
Lowest annual (in 1889) 11. 03 
Greatest in a single month to date (June, 1914) 10. 68 
The conditions just outlined are fairly- representative of those 
obtaining in western North Dakota and western South Dakota. 
Westward, the rainfall gradually becomes less, until in Montana the 
average rainfall diminishes to 15 inches or less, with the exception 
of favored valleys. 
Favorable climatic conditions for maximum plant development 
continued throughout the three years of the experiments herein 
recorded. Annual and seasonal average figures for certain climatic 
data in these years are given in Table I. 
Table I. — Annual and seasonal temperatures, total precipitation, total evaporation, and 
average wind velocity at the Northern Great Plains Field Station, Mandan, N. Dal:., 
during 1914, 1915, and 1916. 
Annual data. Seasonal data (April 1 to August 31). 
• 
Year. 
Average tempera- 
ture. 
Aver- 
Precip-I *&** 
Average tempera- 
ture. 
Precip- 
itation. 
Evapo- 
ration. 
Aver- 
age 
wind 
veloc- 
ity. 
Mean. 
Maxi- 
mum. 
Mini- 
mum. 
itation. 
veloc- 
ity. 
Mean. 
Maxi- 
mum. 
Mini- 
mum. 
1914 
°F. ; "F. 
42 54 
41 52 
39 50 
°F. 
30 
Inches. 
23. 87 
Miles 
per hr. 
6.3 
4.9 
6.1 
°F. 
60 
58 
59 
°F. 
72 
68 
71 
°F. 
48 
47 
48 
Inches-. 
19.04 
19.52 
10.46 
Ivches. 
28. 894 
24. 969 
26. 877 
Miles 
perhr. 
6.2 
1915 
31 1 24.06 
26 15. 07 
6.1 
1916 
6.2 
Average 
41 52 
29 21.00 
5.8 
59 
70 
48 
16.34 
26. 913 
6.2 
TEMPERATURE. 
In 1914 both the annual and seasonal temperatures were slightly 
higher than normal. This, combined with plentiful moisture, pro- 
duced a maximum crop growth. The crops also ripened early and in 
excellent shape. In 1915 the annual average minimum temperature 
was slightly above normal. During the summer months, however, 
cool, cloudy weather was the general rule, and the average mean, 
maximum, and minimum seasonal temperatures were all below 
normal. This resulted in a long growing season: in fact, if the first 
killing frost had not been delayed until October 6. making a frost- 
free period of 142 days as compared with an average of 129 days, 
much damage would have resulted from immaturitv. In 1916 more 
