CLIMATE OF THE SANTA CATALINA MOUNTAINS. 49 
the summer months is almost negligible on the Pacific Coast and grad- 
ually increases on passing eastward until it reaches 50 per cent at Tucson. 
Between Tucson and the Rio Grande it remains at about 50 per cent, but 
from the basin of the Rio Grande eastward the rainfall seasons of the 
Tucson region cease to be a natural division of the year (see table 1). 
Taste 1.—Percentages of summer rainfall and of winter rainfall to the annual rainfall for 
a series of stations stretching from the Pacific coast to the Rio Grande River, through 
southern Arizona. 
Station. Winter. |Summer.! Total. 
Los Angeles, Cal..............5 76.0 Brg 76.7 
Riverside, Cal................. 76.8 2.6 79.4 
Indio, Cakes cccds aac aecreanncacs 73.3 12.0 85.3 
Wenias, Afe.. 5 6 6044.0 sscae nse 59.0 20.3 79.3 
Gila Bend, Ariz............... 47.5 35.5 83.0 
Maricopa, Ariz.............-6- 45.9 34.0 79.9 
Casa Grande, Ariz............. 43.7 37.6 81.3 
Tucson, ATizZ...........000 0 eee 30.7 50.9 81.6 
Benson, Ariz...........0-.0005 24.8 57.5 $2.3 
Bowie, Ariz... ..c0s000sa cannes 34.9 48.5 83.4 
Lordsburg, N. Mex............ 28.3 49.9 78.2 
Deming, N. Mex.............. 22.9 54.8 reer a 
Agricultural College, N. Mex. ..| 17.5 56.8 74.3 
In figure 3 are given curves showing the percentages of the annual 
rainfall which are formed by summer rains and by winter rains for a 
chain of 13 stations stretching from Los Angeles to Mesilla Park, New 
Mexico, on the Rio Grande River. 
TasLe 2.—The total annual rainfall, the summer rainfall, and the percentage of the latter to 
the former for very wet and very dry years at Tucson. 
Eight wet years Eleven dry years 
(14 inches or over). (9 inches or less). 
Years. Years. 
An- Sum- | Per- An- Sum- | Per- 
nual. mer. |centage. nual. mer. |centage. 
1876 nsnewnncicgic ee 14.02 | 10.18 | 72.6 || 1880............. 6.61 | 4.79 | 72.5 
187 8isiwcaovenconae 16.66 | 10.51 | 63.1 || 1883............. 8.48 | 3.03 | 35.7 
ISB) cciianitomndaie 14.92 | 11.98 | 80.3 || 1885............. 5.26 | 2.88] 54.8 
S82 vesieradcvcsaeanrics 15.59 | 9.27] 59.5 || 1886............. 8.02 | 3.97} 49.5 
VS84 sacra te txerschecmare 15.07 | 1.77 | 11.7 | 1891............. 7.78 | 3.44] 44.2 
VS89 55 ond Hiciactea ican 18.37 | 10.84 | 59.0 |) 1894............. 7.14 | 2.61] 36.5 
W890i 2565 5 een seer’ 15.04} 9.04 | 60.1 |] 1899............. 8.38 | 3.72 | 44.3 
W90 Bie tsi wine ene 24.17] 4.50] 18.6 || 1900............. 7.79 | 2.45 | 31.5 
DOOD ears ceronarcaaxeesraed 8.61 | 2.31] 26.8 
WSs csancswvase 8.80 | 5.36] 60.9 
1904 esi cgaccenccs 7.85 | 5.29] 67.4 
Average percentage |.......]....... 53.1 || Average percentage|.......|....--. 47.6 
The fall of approximately half the annual precipitation in the humid 
mid-summer is by no means a constant occurrence at Tucson. In 
1881 the summer rainfall was 80.3 per cent of the annual, and in 1884 
