Jan., 1915.] Predicting Minimum Temperatures. 
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It seems important, however, that some plan be devised 
whereby a fruit man not in touch with the Weather Bureau and 
its maps and forecasts can closely estimate the probable lowest 
temperature at critical periods. 
In investigating this point in connection with our special fruit 
service in Ohio, we have found that the prediction of the minimum 
temperature from the time of the average afternoon median 
temperature gives very close results. 
Figure 1 is a copy of the temperature record made by a self 
recording thermometer at Delaware, Ohio, from May 11 to May 
17, 1914. This shows a rapid fall in temperature beginning at 
about 10 a. m. of the 12th. This was due to a shift of the wind 
to northwesterly and the small change that occurred In the tem¬ 
perature from the afternoon of the 12th to the early morning of 
the 14th was because of continued northerly winds and rainy 
weather. 
Beginning on the 14th, however, and continuing through the 
balance of this week and most of the following week, there was a 
period of clear and comparatively still weather when an area of 
high barometer pressure was centered over this district. Under 
these conditions the temperature rises high during the daytime 
under strong sunshine, and then falls quite low at night under 
free radiation. It is under conditions of this kind that frosts 
may be expected in the spring and fall. It will be noticed that 
the rise in temperature is rapid in the early forenoon and that the 
thermograph curve has a decidedly convex shape. 
The highest temperature will be reached at about 3 o’clock 
in the afternoon. The temperature will fall slowly for two or 
three hours, then there will be a rapid fall in the evening and 
a slower fall until the lowest point just before sunrise. The 
afternoon curve has a decided concave shape. There is a marked 
similarity in the curves during these days when frosts threaten. 
This being true the question was raised whether the half way 
point in the temperature fall from the maximum of one day to 
the minimum of the next morning might not occur at about 
the same time each evening. 
A study of available records showed that in May the half 
way temperature occurred at Delaware on an average at 7:36 
p. m. and that the variations on either side of this time was less 
than 20 minutes in either 1913 or 1914. 
For example the highest temperature at Delaware on May 14, 
1914, as shown by the thermograph record in Figure 1, was 65. 
The temperature at 7:36 p. m., the average time of the median, was 
51. Subtracting this from the maximum leaves 14. If we take 
14 from 51 then we shall have 37 as the predicted minimum 
temperature during the coming night, by this method. The 
lowest temperature that actually occurred was 36 or only 1 lower 
than estimated. 
