Gulf of California — Roden 
27 
CLIMATOLOGY 
The great differences in climatic conditions 
observed in the Gulf as one proceeds from 
northwest to southeast, covering nearly nine 
degrees of latitude, and the differences that 
exist between the east side and the west side 
of the Gulf, are closely related to the atmos- 
pheric circulation and to the existence of 
mountain ranges that modify this circulation. 
The influence of the Pacific Ocean upon 
the climate of the Gulf is greatly reduced by 
a nearly unbroken chain of mountains, 2000 
to 3000 m. high, in Baja California. The con- 
siderable differences in temperatures and pre- 
cipitation between the Pacific side and the 
Gulf side have already been mentioned by 
Thorade (1909) and are fully confirmed by 
data collected by the Servicio Meterologico 
Mexicano (Boletin Anual) . Along the Pacific 
side of the peninsula the air temperatures are 
never excessively high and precipitation falls 
during the winter season in the northern part, 
and during the summer season in the southern 
part, with annual amounts around 200 mm. 
Along the Gulf side air temperatures are very 
high in summer and rather cool in winter. In 
the north all the precipitation falls in sum- 
mer. The amount of rainfall (Table 1) varies 
between traces in the north and 200 mm. at 
the southern tip of Baja California, which is 
crossed by the Tropic of Cancer. The rainfall 
on the corresponding latitude on the eastern 
side of the Gulf amounts to 400 mm. per year. 
On the average the west coast of the Gulf 
receives only half as much rain as the east 
coast. In Sonora the winter is cool and the 
summer hot. Precipitation falls from July to 
September, varying between traces in the 
northernmost part and 251mm. in Guaymas. 
In Sinaloa the winter is warm and the summer 
less hot than in Sonora. Precipitation falls 
from August to October, with amounts be- 
tween 300 mm. in the north and 850 mm. in 
Mazatlan (Table 1). From the discussion of 
the precipitation figures it becomes evident 
that the Gulf of California is far from being 
situated in a desertlike environment. 2 The 
vegetation in Baja California and Sonora is of 
2 Most Americans call northern Sonora and Baja 
California a desert, though people from North Africa 
and South America would consider this region a dry 
steppe. 
TABLE 1 
Mean Monthly Air Temperature and Precipitation 1921-1935 (Serv. Met. Mex., Boletin Anual) 
WEST COAST (IN GULF) 
EAST COAST (iN GULF) 
EAST COAST (OUTSIDE GULF) 
Mulege 
La Paz 
Guaymas 
Topolobampo 
Mazatlan 
Cabo 
Corrientes 
(26°53'N- 
(24°10 / N- 
(27°55'N- 
(25°36'N- 
(23°H'N- 
(20°24 / N- 
112°00'W) 
110°18'W) 
110°53'W) 
109°03'W) 
106°25 , W) 
105°43'W) 
Temp. 
Prec. 
Temp. 
Prec. 
Temp. 
Prec. 
Temp. 
Prec. 
Temp. 
Prec. 
Temp. 
Prec. 
°C. 
mm. 
°C. 
mm. 
°C. 
mm. 
°C. 
mm. 
°C 
mm. 
°C. 
mm. 
January . . . 
14.0 
2.6 
18.2 
3.2 
17.7 
7.9 
18.6 
6.4 
19.3 
11.0 
23.2 
19-5 
February . . 
16.0 
3.4 
19.2 
11.4 
18.9 
6.3 
19.7 
6.6 
19.4 
9.7 
22.9 
29.6 
March .... 
17.8 
0.1 
21.3 
0.8 
20.7 
4.6 
20.1 
6.4 
19.7 
3.4 
22.7 
1.3 
April 
20.1 
0.2 
23.2 
0.2 
22.8 
3.0 
22.2 
tr. 
21.3 
0.1 
23.9 
tr. 
May 
22.9 
0.1 
25.5 
tr. 
25.5 
2.8 
25.0 
1.8 
23.8 
1.8 
25.4 
2.3 
June 
27.2 
tr. 
27.2 
0.2 
28.8 
0.7 
29-1 
5.3 
26.4 
29.2 
26.7 
57.3 
July 
30.5 
6.1 
30.0 
6.3 
30.7 
46.7 
29-8 
39-9 
27.5 
166.9 
28.9 
145.0 
August. . . . 
30.4 
16.8 
30.3 
41.7 
30.5 
75.5 
29.7 
100.6 
27.6 
241.8 
27.9 
272.1 
September. 
29.0 
40.0 
29.0 
51.9 
30.2 
54.4 
29.7 
55.9 
27.5 
268.6 
27.5 
307.0 
October. . . 
24.6 
5.4 
27.0 
9.6 
27.3 
9.5 
27.8 
73.7 
26.7 
61.6 
27.5 
91.0 
November. 
19.5 
6.8 
23.2 
13.4 
22.6 
11.1 
24.0 
7.0 
23.5 
11.7 
26.1 
15.2 
December . 
14.9 
19.2 
20.0 
34.3 
18.6 
28.9 
19.7 
55.3 
20.6 
44.4 
23.8 
13.5 
Year 
22.2 
101.1 
24.4 
173.0 
24.5 
251.4 
24.6 
358.9 
23.6 
850.2 
25.5 
953.8 
Minimum . 
0.0 
— 
0.0 
— 
7.0 
^ . 
8.0 
''Epc 
11.2 
flB 
12.0 
Maximum . 
41.9 
— 
40.5 
— 
47.0 
— 
41.1 
/■' — \ 
33.4 
— 
43.8 
— 
