46 MASS. EXPERIMENT STATION BULLETIN 402 



Table 3. — Rainfall During the Week Before the More Harmful 



Cranberry Frosts Compared With the Normal Rainfall for the Period 



— Wisconsin 

 (In Inches) 



Meadow Neillsville Wisconsin Average 



Valley Rapids 



Week Preceding Frost 



Rain- Nor- Rain- Nor- Rain- Nor- Rain- Nor- 



fall mal fall mal fall mal fall mal 



Aug. 17 to 23, incl., 1891 1.30* .74 1.25* .82 1.61* .78 1.39* .78 



Aug. 23 to 29, incl., 1893 03 .74 .08 .82 .00 .78 .04 .78 



Aug. 14 to 20, incl.. 1895 04 .74 .47 .82 .20 .78 .24 .78 



June 23 to 29, incl., 1900 15 1.00 .00 1.11 - - .08 1.06 



June 4 to 10, incl., 1903 02 1.00 .55 1.11 .31 .98 .29 1.03 



Aug. 1 to 7, inch. 1904 19 .74 .26 .82 .60 .78 .35 .78 



Aug. 26 to Sept. 1, incl., 1909 37 .76 .12 .83 .53 .79 .34 .79 



June 2 to 8, incl., 1913 31 1.00 .00 1.11 .30 .98 .20 1.03 



July 12 to 18, incl., 1929 20 .82 .15 .89 .40 .75 .25 .82 



* This rain broke a well-established drouth. 



All the widely destructive cranberry frosts in Massachusetts (Table 1) except 

 those of June 6, 1879, September 30, 1888, May 13, 1895, and late April, 1910, 

 were preceded by a week with rainfall much below normal for the time of year. 

 The 1888 frost came (Table 4) after a period of extremely unseasonable cold 

 had reduced the heat of the soil. The rains before the 1879, 1895, and 1910 

 frosts broke drouths and may well have failed to restore normal moisture in the 

 soil. The Wisconsin records (Table 3) have only one instance of a very harmful 

 frost without a marked deficiency in rainfall during the preceding week, the rain 

 in that case breaking a drouth and probably failing to restore normal soil moisture. 

 Some of the severe New Jersey frosts (Table 2) have come after excessive rain- 

 fall, this probably due largely to the lack of sand and the heavy vine and weed 

 growth common on the New Jersey bogs.*^ The greater evaporation and trans- 

 piration under the higher temperatures in New Jersey were also a factor. 



In the frost seasons in the Cape cranberry district since 1911, no night with 

 dangerously low temperatures has occurred within a day or two after an inch and 

 a half of rain at the cranberry experiment station, unless the rain broke a drouth. 

 Three successive dangerous frost nights within five days after such a rain have 

 never been observed in this period at any time, and two such nights in succession 

 have not occurred from June to September, inclusive, under these conditions. 



Much water in the soil tends to prevent a large fall in temperature during the 

 night because the water vapor taken up by the air from the wet ground lessens 

 cooling^^ and because water, a twenty times better conductor of heat than air, 

 greatly improves the conductivity of the soil when it replaces the air in it,^" 

 giving a faster flow of heat into the ground when the sun is shining and a faster 

 flow from the ground at night. -^^ Also the specific heat of a wet soil is much 

 greater than that of a dry similar soil at the same temperature. The specific heat 

 and conductivity of the topsoil rather than its temperature alone are the impor- 

 tant factors here, and their influence depends greatly on the water content of 

 the soil.^^ So most soils, including sand-covered cranberry bogs, are less likely 

 to permit frost formation when wet than when dry. 



^^Peat is a poor conductor of heat even when wet. U. S. Monthly Weather Rev. 67:440, 1939. 

 (Copy in the Middleboro library.) 



See the discussion of the relations of cranbeiry vine growth to the frost hazard on pages 49 

 and 50 of this bulletin. 



49Young, op. cit., p. 7. 



^"Geiger, op. cit., pp. 6-8. 



^'Schoonover, Brooks, and Walker, op. cit., p. 23. 



^^Brunt, op. cit., pp. 138-141. 



