HAIL INSURANCE ON FARM CROPS. 
13 
Some idea of the relative importance of the hail hazard in differ- 
ent parts of the country may be obtained from figure 3, which indi- 
cates in a general way the -frequency of the occurrence of hail in the 
United States during the four months, May, June, July, and August. 
The data represented on this map are based on reports from the vari- 
ous United States Weather Bureau stations, and cover the 14-year 
period 1906-1919, inclusive. The map or chart in question, it should 
be emphasized, indicates only the average annual frequency of the 
occurrence of hail during the months stated, no attempt having been 
made to allow for differences in the severity or the ctestructiveness 
of hail storms. It should perhaps also be pointed out, as has been 
done b}' the Weather Bureau in connection with earlier published 
Hf^ 
»o 
AVERAGE NUMBER OF DAYS WITH HAIL 
MAY TO AUGUST INCLUSIVE 
__^_^ 1906 1919 
1 
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N° V-^> 
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A. ^, 
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^W weather BUREAU, u S Da 
Fig. 3. 
data on this subject/ that the reports on which the chart is based 
come from only 167 stations rather unevenly distributed throughout 
the United States. Since hail storms are frequently very local in 
character, it follows that the data as represented embody an element 
of chance even as to the average frequency of hail. It is probable, 
for example, that the total number of times at which hail occurred 
and, hence, also the average yearly number of such occurrences re- 
ported from a given station, may represent either more or less than 
the average frequency for all parts of the area for which such station 
is considered a center. 
To a certain extent the relatively long period of time covered by 
the reports will, of course, tend to eliminate some of the chance ele- 
ments involved in the lack of a sufficient number of reporting stations. 
See Weather Bureau Review for March, 1917, pp. 94 et seq. 
