CONTENTS. V 



The Climatic Conditions of the United States— continued. page, 



II. Temperature conditions — continued. 



2. Intensity of temperature conditions — continued. 



G. Absolute temperature minima (plates 41 and 42) 234 



H. Average daily normal temperature for coldest 14 days of year 



(table 8, plate 43) 237 



Table 8. — Average normal daily temperatures for 



coldest 14 days of the year 238 



1. Merriam's mean normal temperature for hottest six weeks of 



year (plate 44) 242 



J. Normal mean annual temperature, U. S. Weather Bureau 



(plate 45) 242 



3. Conclusions from the study of temperature conditions 244 



III. Moisture conditions. 



1. Introductory 246 



2. Supply of water to the plant . 



A. Preliminary considerations 247 



B. Precipitation. 



(1) Introductory 249 



(2) Normal mean daily precipitation for period of average 



frostless reason {P/S) (table 11, plate 46, and fig. 2) 250 

 Table 11. — Precipitation and evaporation data for 



the period of the average frostless season 253 



(3) Total normal precipitation for period of average frost- 



less season plus preceding 30 days, divided by number 



of days in average frostless season (t/5) (table 11) . . 260 



(4) Number of normally rainy days in period of average 



frostless season (table 13, plate 47) 260 



Table 13. — Number of days in period of average 

 frostless season with normal precipitation of 

 more than 0.10 inch and with normal precipita- 

 tion of 0.10 inch or less, the latter also expressed 

 as percentage of the number of days in the aver- 

 age frostless season 264 



(5) Number of normally dry days in period of average 



frostless season (table 13, plate 48) 266 



(6) Percentage of days in period of average frostless season 



that are dry days (with normal daily precipitation of 



0.10 inch or less) (table 13, plate 49) 267 



(7) Length of longest normally rainy period in period of 



average frostless season (table 14, plate 50) 267 



Table 14. — Beginning, ending, and duration of 

 each normally dry period and of longest 

 normally rainy period within period of average 

 f ro.stless season 272 



(8) Length of longest normally dry period in period of aver- 



age frostless season (table 14, plate 51) 279 



(9) Normal annual precipitation, after Gannett (plate 52) 279 

 (10) Conclusions from study of precipitation conditions ... . 281 



3. Removal of water from plant. 



A. Introductory. 



(1) General control of water-loss 283 



(2) Atmospheric evaporating power 284 



Vapor-tension deficit 287 



Relative humidity 288 



Wind 289 



(3) Absorbed radiation 290 



B. Atmospheric evaporating power in the United States . 



(1) Very limited nature of available data 291 



(2) Russell's data of evaporation in the United States .... 292 



