234 



ENVIRONMENTAL CONDITIONS. 



Houghton, Mich 103 



Ishpeming, Mich 98 



Escanaba, Mich 100 



Billings, Mont 112 



Havre, Mont 108 



Chicago, 111 103 



Cairo, 111 106 



Vicksburg, Miss 101 



Natchez, Miss 105 



New Orleans, La 102 



Galveston, Tex 98 



Silver City, N. Mex 103 



Tampa, Fla 100 



Miami, Fla 96 



The area characterized by maxima of less than 100° F, comprises 

 northwestern Washington and coastal points on the Pacific north of 

 about the fortieth parallel of north latitude, central Idaho, western 

 Montana and Wyoming, northern Minnesota, northwestern Wis- 

 consin, and the entire northern peninsula of Michigan, some of the 

 western and not so much of the eastern margin of the southern penin- 

 sula of the last-named State, eastern Ohio, the northern half of Pennsyl- 

 vania, the Appalachian area south of about the thirty-eighth parallel, 

 all of New York, the western half of New England, Atlantic coastal 

 stations from southern Maine to North Carolina, the southern third of 

 Florida, and a few coastal stations on the Gulf of Mexico. Besides the 

 area thus described, there are several restricted areas of maxima below 

 100°, the main ones of which occupy the regions of the Sierra Nevada 

 and of the Rocky Mountains. It is thus clear that only a very small 

 portion of the United States has been characterized, during the periods 

 of record, by maxima below 100° F. 



The area characterized by maxima of 110° or above comprises local- 

 ized sections, the main ones of which are as follows: (1) the southern 

 third of California, the great Sacramento-San Joaquin Valley, and 

 Arizona south of the great plateau; (2) western Texas and the Rio 

 Grande region; (3) southwestern North Dakota, northwestern and 

 southeastern South Dakota; (4) western Kansas, south central Ne- 

 braska and northwestern Oklahoma ; (5) northeastern Arkansas, south- 

 eastern Missouri, southwestern Illinois, and a little of northeastern 

 Missouri, and southeastern Iowa. 



It seems clear that the variation in absolute maxima throughout the 

 country is so slight that this criterion can be of no practical use for our 

 present purpose. Of course, it is patent that the lengths of the periods 

 of observation are very unequal for the different stations, and it seems 

 probable that, with much longer periods, the absolute maxima will 

 approach about 110° F. for approximately the whole country. 



(G) ABSOLUTE TEMPERATURE MINIMA. (PLATES 41 AND 42.) 



A chart of the absolute minima of temperature (as these are given 

 in the Summary by Sections) was prepared in the same manner as was 

 that of the absolute maxima. This chart brings out some rather 

 definite climatic relations, and appears to be valuable for our purpose ; 

 it is therefore here reproduced as plate 41. The Fahrenheit intervals 

 have been so chosen in the making of this chart that they correspond 



