14 BULLETIN 1409, U. S. DEPARTMENT OF AGRICULTURE 
west across the flat country until they reach the Andes and then turn 
due north or northeast. The annual mean temperature of the entire 
country is 58° F. The 68° line corresponds roughly with the thirtieth 
parallel of latitude, running nearly due west in the northern third 
of the country until it reaches the mountainous region in the north- 
west where it turns at right angles and runs east of north to Bolivia. 
(See fig. 3.) 
WINDS 
With respect to winds, Argentina may be divided into two great 
regions with the forty-second parallel of latitude as a dividing hue, 
crossing the northern part of Patagonia near the boundary between 
the Territories of Kio Xegro and Chubut. South of this line the 
winds blow steadily from the west over and through the deep passes 
of the Andes. North -of this line the winds are variable, but generally 
from the east or north. Winds from the south and southwest, 
which often come with great suddenness, are called '"Pamperos'' and 
usually the temperture falls rapidly. The pamperos come with 
great velocity and are accompanied by turbulent-looking clouds and 
violent electrical discharges. Just before a pampero the weather is 
usually oppressive, and following the pampero it is usually clear and 
very agreeable for several days. There are occasional winds of 
hurricane force which blow off roofs and uproot trees. The effect 
of strong east or southwest winds in changing the level of the La 
Plata River has been mentioned. Apparently little or no damage is 
caused by the violent electrical discharges that accompany the 
pamperos. 
RAINFALL 
Rainfall in the extreme north of the Republic in summer is sub- 
tropical averaging about 16 inches. In the far south and along the 
South Andes the rainfall is heavy from the condensation of the 
moisture brought by the west winds which cross the Andes without 
losing as much of their moisture as they do farther north. Rainfall 
ranges from 20 to do inches annually. The zones of heavy, light, 
and scant rainfall generally run nearly north and south. (See fig. 4.) 
The line of 40-inch average rainfall begins north of the city of Buenos 
Aires and runs west of north to the western part of Paraguay. The 
triangular area to the east of this line is probably 300 miles across 
in the widest place and 600 miles long. The rainfall becomes heavier 
east of this line until in the Territory of Misiones in the extreme 
northeast it is about 70 inches. The line of 20-inch average rainfall 
is from 250 to 350 miles west of the 40-inch zone and includes the 
great cereal region of Argentina in which more than 90 per cent of the 
total agricultural production of the country is found. The line of 
10-inch rainfall is from 50 to 150 miles west of the 20-inch zone and 
runs slightly west of north. To the west of this is the semiarid zone 
with less than 10 inches, which is about 200 miles wide and 2,000 
miles long. Farther south and west in Patagonia the rainfall becomes 
heavier up to 20 or more inches. In the north-central portion of 
Argentina there is a small area in Tucuman. perhaps 50 by 100 miles, 
with an average rainfall of 40 inches, and another small area farther 
north in Jujuy with an average rainfall of 25 to 30 inches. 
