8 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1917. 



CLIMATE. 



The climate in this region is characterized by a long, warm grow- 

 ing season; a shorter cooler season, during which frosts occur; and 

 a scanty supply of rain, insufficient to insure crops without irriga- 

 tion. Two so-called wet seasons occur, one in the spring and one in 

 late summer. Except for the hot summer months the climate imyj be 

 said to be exceptionally pleasant and favorable for the production of 

 crops. 



The weather records kept at various places in and near the area 

 are incomplete. In some instances statistics are available for only 

 a short period of years, although Casa Grande and Maricopa have 

 kept partial records since 1876. The data nevertheless indicate in 

 a general way the conditions of temperature and rainfall. Phoenix 

 is representative of a large region of which the area surveyed is a 

 part. The mean annual precipitation at Phoenix for 8 years, from 

 1896 to 1903, inclusive, was 6.8 inches. The average number of days 

 with a precipitation of 0.01 inch or more was 34 per year. The pre- 

 cipitation for the driest year was 3.7 inches and for the wettest year 

 12.8 inches. At Maricopa, about 5 miles southwest of the area, on 

 the open desert or plain, the mean annual precipitation for a period 

 of years extending from 1876 to 1907, except 1878 and 1879, was 

 6.06 inches. The amount for the driest year recorded (1900) was 

 2.09 inches, and for the wettest year (1905), 13.51 inches. The table 

 below, compiled from records of th^ Weather Bureau, shows the 

 mean annual, seasonal, and monthly rainfall and temperature, the 

 maximum and minimum temperatures, and the rainfall for the 

 wettest and driest years. 



Normal monthhj, seasonal, and annnal temperature and preciiyitation at 



Maricopa. 



