372 



FUNDAMENTALS OF FRUIT PRODUCTION 



is, in any case, sufficiently complex to warrant the grower who wishes 

 reliable forecasts in trying to secure them from the nearest station of the 

 Weather Bureau, either directly or by corrections from forecasts made 

 for some noar])y point. 



Local Interpretation of "Key Station" Predictions. — It will be under- 

 stood, considering the local differences in temperature, that the general 

 forecast may require correction for the grower's own site. The forecast, 

 as issued, is based upon observations from sheltered instruments at 

 a certain spot; yet it is given out necessarily to cover a wide radius of 

 territory where local differences may be considerable. Districts that 

 are well organized for frost fighting have several "key stations" for which 

 the forecasts are corrected individually. Even in such cases, however, it 

 may be necessary to make discriminating corrections if the probable 

 minimum for a given spot is to be determined. 



Table 72 shows minimum temperatures on cold spring mornings at 5.5 

 feet and 0.5 foot elevations at three spots in the village of Williamstown, Mass. 

 Station A is a shelter thermometer and may be considered the "key station." 

 It is of interest to see how predictions for the key station would apply to straw- 

 berries at Station 7. As is shown in the last column of the table the difference is 

 variable but always considerable, under conditions favorable to frost. As 

 Milham,!^^ from whose data the table is taken, states, it is not a difference due 

 to site alone; in adapting the forecast for Station A to vegetation at Station 

 7 allowances must be made as follows: 2° for the deviation between sheltered 

 and exposed thermometers, 3° for the inequality in height of the two thermome- 

 ters above ground and 6° for the difference in site. These together indicate a 



