THE WEATHER 



Since the year 1908, the Weather has not been given separate con- 

 sideration in the Annual Report. Although general climatic conditions 

 necessarily remain the same, it seems well to mention again, as a pre- 

 face to the 1916 report, those factors which determine the climate of 

 iVrizona — climate meaning the conditions of its atmosphere as regards 

 heat or cold and moisture or dryness, manifested in a succession of 

 weather changes throughout the year. 



Arizona lies between the 31st and 37th parallels north latitude. 

 This geographical location gives, at lower altitudes within the State, a 

 semi-tropical temperature, characterized by hot summers and short 

 temperate winters. As there is no large body of water contiguous to 

 any part of its area, and none of the moisture-laden breezes from the 

 j^acific reach Arizona because of intervening mountains, the region, as 

 a whole, has what is termed an inland, arid climate. The air is very 

 dry and the precipitation slight. Southern Arizona is the only section 

 of the United States having more than 80 percent of the possible amount 

 of sunshine. Temperature, as a rule, decreases 3 degrees F. for every 

 1000 feet of elevation above the sea level, and precipitation increases 5.8 

 inches for every 1000 feet. Arizona, therefore, with its altitudes vary- 

 ing from less than 90 feet in the Colorado Valley to nearly 13,000 feet 

 on the highest mountain tops, shows great differences in temperature 

 and precipitation in various localities. 



The Weather Bureau of the U. S. Department of Agriculture re- 

 cords the climatological data for 144 different places in Arizona. 

 (Obviously so complete a report is not possible in this brief discussion. 

 Kingman, Flagstaff, and the Prescott Dry Farm in the northern half ; 

 the Yuma Date Orchard, Phoenix Weather Bureau, the State University 

 at Tucson, and the Cochise Dry Farm in the southern half of the State, 

 have been chosen as representative points because of their locations and 

 differing altitudes, and because of the connection of the five latter with, 

 or proximity to agricultural work carried on by the Experiment Station. 

 The following tables have been compiled from data published by 

 the U. S. Weather Bureau. Table XXVIII records climatological data 

 for the past eight years and in a measure brings up to date the discussion 

 in the Nineteenth Annual Report. It serves as the basis for some 

 generalizations concerning the climate of the State, and also for noting 

 the departures from normal, if any, for the year 1916. 



