WEATHER AND^CRANBERRY PRODUCTION 51 



Add 2 degrees to the computed temperature when the 7 p.m. wind velocity at 

 Worcester is over 7 miles an hour and the barometer does not rise more than .07 

 of an inch from 4 to 8 p.m..; but subtract 1 degree if the wind velocity at Wor- 

 cester is not over 9 miles an hour and the barometer rises more than .08 of an 

 inch from 4 to 8 p.m. If, as sometimes occurs in April and October, the barometer 

 rises .15 of an inch or more from 4 to 8 p.m. with the wind velocity at Worcester 

 not over 7 miles an hour at 7 p.m., subtract 2 degrees. 



NOTES:-In predicting, it is best to average the results of the different formulas 

 in each period. 



If at any time in the frost seasons the 7 p.m. dew point at Worcester, Carlisle, 

 Milton, or Gloucester is below 20 degrees, the chances are 5 to 1 that the mini- 

 mum temperature will also fall below 20 degrees on some bogs in the cranberry 

 district. 



Temperatures on cold clear nights on most of the Massachusetts cranberry 

 bogs fall at an average rate of about one degree an hour till sunrise after it has 

 been calm for two hours. 



A clear sky in the evening at all or most of the observing stations is good evi- 

 dence that it will be as cold as other data indicate. A damaging frost rarely 

 occurs when it is entirely cloudy at all inland stations and partly or entirely cloudy 

 at East Wareham at 7 p.m., unless the barometer rises sharply from 4 to 8 p.m. 



Wind direction is generally of litcie value in frost predicting on Cape Cod; 

 but, if the wind is from the north or northwest at East Wareham at both noon 

 and 7 p.m. (E.S.T.), it is especially likely to be as cold as other conditions indi- 

 cate it will be.* The barometer usually rises sharply in the evening with this 

 wind condition. A west wind in the evening is probably safer than any other. 



*Weather forecasting in the United States. W. B. No. 583, 1916, pp. 199, 201, and 208. 

 The more severe frosts on Nantucket usually come with a dying easterly wind. 



