10 BULLETIN 1287, U. S. DEPARTMENT OF AGRICULTURE 
average wind velocities of the year usually occur. These often do 
much damage by soil blowing. The highest monthly average wind 
velocity recorded at the station was 10.4 miles per hour in April, 1919. 
June and July are generally months of comparative quiet in atmos- 
pheric movement, and August usually shows less wind, movement 
than any other month of the year, the velocity averaging little more 
than 5 miles per hour. Hot winds are almost unknown in this 
section. September and October are usually very variable as to. 
atmospheric conditions, winds sometimes occurring of sufficient 
velocity to start considerable soil movement. There are compara- 
tively few periods of high wind velocity in November and December, 
but those which occur generally accompany snowstorms and may 
result in severe blizzards. 
TaBLE 3.—Monthly evaporation from a free water surface at the Akron Field Station 
from April to September of each year from 1908 to 1922, inclusive 
[Evaporation and precipitation data in inches] 
Ev ati 
aporation | acer. Ratio of 
pl- =~ 
: ereet | tate | ereePl 
BEE | Seasonal,| Apr. to ‘a@lon to 
| Apr. | May June July Aug. | Sept. | Apr. to Sept. ae as 
| Sept. os 
| | | 
TADS ag So es Se es 4.740 | 7.709 | 7.637) 8.474) 7.826] 8.550 44, 936 | 11.31 1:3. 97 
TS OE) oe Sr cee te rete 4.734 | 6.825 | 7.003 | 9.396 | 8.5388] 5.857 42. 353 | 16. 13 1:2. 63 
OT O Se ee ee 62387, foroaton | Seeenl no ekOs) eeiea2n eros okO 43. 621 | 16. 40 1:2. 66 
TYG) bce a a Se ey | 5.841 | 7.323 | 9.753 | 9.774; 8.944] 7.183 48. 818 10. 30 1:4. 74 
GW IAS, gel as enn en es Bee pe 4.5385 | 7.097 | 6.750 | 7.618 | 7.048] 4.648 | 37.696 15. 78 1:2. 39 
TIS se Cee ee 4.330 | 5.840 | 8.180 | 9.260 9.310 | 6.040 42.960 10. 05 1:4. 27 
OVARY S Seas Sas 4.290 | 5.608 | 7.509 8.654 8.364] 7.438 | 41.863 11.95 1:3. 50 
TUE WG ga Aree bec 4.220 | 5.033 | 5.883 | 6.660 | 5.961 | 5.793| 33.550 19. 44 ier 
OT G Bee eee OS Fa ae | 6.208 | 7.811 7.979 | 11.116 | 7.216 | 6.836 47. 166 10. 77 1:4. 38 
Ope ee ee Oe | 4.081 | 4.930} 8.424 | 10.186 | 8.464] 6.624] 42.709 14. 80 1:2. 89 
TPH IS) SO oe a a Ni 4.102 | 6.780 | 9.329 | 9.252; 7.676 | 4.283 41. 422 16. 81 1:2. 46 
1 eS a eee (eee ees ee Cals | 10.282 | 9.718] 6.144 47. 232 10. 67 1:4. 43 
GD (gee ie ee ee | 4.786 | 6.840] 6.961 | 8.582 | 6.918 | 6.825 40. 912 18.12 1:2. 26 
Gp (2 =e s OE BE EN Lees 5.505 | 6.245 | 7.773 | 10.708 | 8.594] 7.078; 45.903 9.15 1:5. 02 
TOD Dim meee foe ee 4.276 | 6.792 | 8.225 | 9.200 | 8.853 7. 233 44, 579 | 13. 55 123229 
Average : ener = 4.866 | 6.534 | 7.926 | 9.262 | 8.038 6. 423 43. 048 13. 68 1:3. 14 
TEMPERATURE 
The temperatures at the station are recorded daily throughout the 
year by means of maximum and minimum thermometers, supple- 
mented by a thermograph. The nights at Akron are cool during the 
entire year. The winter temperatures, although low, are not so low 
nor are the summer temperatures so high as in most parts of the 
northern Great Plains. The cool summer temperatures are due to 
the high elevation. The absolute minimum during the period is 
—28° F., recorded December 8, 1919, and the absolute maximum is 
103° F., recorded July 30, 1913. The temperature has not been a 
limiting factor in the yields of most of the cereals. The grain 
sorghums were frosted several times before they were fully mature, 
but the development of earlier maturing strains possibly will eliminate 
this danger. During some years winter wheat was injured by low 
temperatures, but injury by cold is unusual unless the low tempera- 
tures are accompanied by other factors, such as low moisture supply 
or high wind velocity. , 
The dates of the last killing frost in the spring and the first in the 
autumn for each year are shown in Table 4. Unless otherwise 
stated, a temperature of 32° F. is recorded as frost, although on 
