Argentina extended for 38 degrees in the meridian sense, starting from 22 ° lat. S., and with mountain ranges up to 7000 m., Necessarily encloses within its borders very different climatic provinces. However, the characters of these are framed within certain general lines deriving from the position of the territory between two oceans, from its shape and from that of the continent that is shrinking from N. to S., and from the presence of a very high system of mountains along the western margin. In the first place, with respect to the distribution of atmospheric pressure and winds, there is a fairly clear division into two large sections: a northern one, from about 22 ° to 42 ° parallel, with periodically variable winds as a consequence of the changing seasons, under the ‘ influence of humid Brasilia covered with thick tropical and subtropical vegetation; and another southern one, essentially comprising Patagonia, permanently swept by strong winds of mainly western origin. In the northern section, the winds blow from the east in the summer, reversing in the winter. Between the two sections, in the intermediate transition zone, unbalances naturally arise, with the recall of air from S. to N., which give rise to characteristic winds, such as the well-known pampero, fresh SW wind, which at times moderate mitigates summers on the edges of the Plata estuary, but some other violently hits the Pampa, raising black clouds of dust that obscure the sky (tormentas, hurracanes, torbellinos). Or like the “Norte” wind that blows very hot precisely from N., and that in the innermost provinces, located in the driest part, such as San Juan and Mendoza, blows exhaustingly and has received the name of zonda. On the vast plain of the Pampa, the more or less strong wind blows perennially, and indeed the lack of arboreal vegetation that characterizes it has been attributed to this. Further to S. in Patagonia the violence of the winds is such as to create even a serious obstacle to navigation over those lakes, which have perpetually agitated waters.
The rainfall regime is connected with the direction and origin of the winds, and consequently oscillates between that of the summer tropical rains at an almost fixed date, dominant in the NE., And that of the variable rains, with winter maximums. But more important than the seasonal distribution is the quantity of rainfall oscillating over the vast surface between very distant limits, from 2000 mm. almost to zero. Characteristic is the trend of the isoieties (lines that join the points of equal average annual precipitation height), which mostly have a direction very close to the meridian one, so that the areas between two isoieties, run significantly parallel to the greater dimension. of the country, almost from N. to S.
In general, the maximum precipitation lines, above 1000 mm. yearly, they are close to the two main sides of the town; the most important area of heavy rainfall is located along the border of Brasilia, west of the river line formed by the Plata-Paraná-Paraguay. To find another one, incomparably smaller, with equal or greater rainfall, you have to go below 37 ° lat. S., along the opposite western Chilean border, passing through the Cordillera, where, up to the Strait of Magellan, the areas of heavy rainfall, which characterize the Pacific side of the great southern chain, occasionally penetrate the Argentine territory in long and narrow strips. -American. The area of scarce precipitation (between 250 mm. And 0) begins at N. della Puna, where there are sometimes periods of several years without any rain, and descends parallel to the Andes, towards S., embracing the Precordigliere and the western side of the Sierre Pampeane (Desaguadero valley), widening more and more until it reaches the sea at the mouth of the Colorado and cover further to the South. all the Patagonian plateaus up to the northern foot of the hills which accompany the Strait of Magellan. On either side of this arid meridian zone, rainfall is increasing rapidly but in thin strips towards the West, where the Andes are; over very large areas, which include the most inhabited and fertile part of the republic, towards the east.
The only exception to this general trend in the superficial distribution of precipitation is an isolated area of heavy rainfall that goes from Tucumán to Jujuy, with a very elongated shape, and where in some places it exceeds 1000 mm. of fall. This area gives rise, in the middle of the dry climate territory, to a kind of verdant oasis, that of the province of Tucumán: the only one in Argentina that grows sugar cane in large, and in which the vegetation takes over short distances the most diverse characters, from the straight tropical to the temperate; in order to have compared that happy place to a magnificent park or natural botanical garden. Undoubtedly, the presence of the Sierra de Aconquija, which, immediately west of Tucumán, has greatly contributed to creating these conditions. it rises with peaks higher than 5000 m., almost without transition, on the central Argentine plane. Another notable feature of precipitation in the flat part of Argentina is its extreme variability from one year to the next. Thus in Buenos Aires itself, close to the limit between Brasilia and Pampa, with an average annual precipitation of 930 mm., Dry vintages with 547 mm. (1893), and humid with over 2000 mm. (1900). and humid with over 2000 mm. (1900). and humid with over 2000 mm. (1900). For Argentina 2012, please check oxfordastronomy.com.
The irregularity of rainfall, and its scarcity in certain parts of the country, since the colonial period, has given rise to a wise economy of water for agricultural purposes, and to ingenious irrigation systems to make possible certain crops, which otherwise would not. they would have been. For example, in San Juan and Mendoza, two wine provinces, the vine is an irrigated crop. In modern times, grandiose systems have been created for this purpose, such as the aforementioned Neuquén dam, to irrigate the Río Negro valley, and the well-known San Roque reservoir, in the Río Primero valley in the Sierra Chica de Córdoba, with 400 million of mc. of capacity.
For the temperature, considerations similar to those of the other climatic factors apply, extending Argentina from the torrid zone to the squalid solitudes of Tierra del Fuego, where the glaciers end up in the sea. Although latitude and altitude visibly influence the trend of the annual isotherms, which in the lower and flat part follow the parallels more or less proximately, and instead assume an almost meridian trend along the Cordillera, no less evident is the adherence of the extreme value of the summer and winter averages, to the trend of the intermediate longitudinal zone of minimum precipitation, which extends from the Puna to the Desaguadero valley to most of Patagonia. In this area of little or no rain there are maximum and minimum temperatures, and above all the maximums of thermometric excursions, both annual and diurnal. In fact, the area of maximum summer temperatures corresponds to an area surrounded by a closed curve, included in the lower part of the provinces of Catamarca, La Rioja, and San Juan, where the January average is 30 °, so high as to constitute, according to meteorologists, the hottest area in South America, although, to be a few degrees S. of the tropic, it is completely outside the torrid zone. Around this area, temperatures are decreasing both towards the north and towards the south, but in the latter direction the isotherms corresponding to January all have a characteristic cusp towards the south when they cross the arid northern belt.
For the same reasons, in the dry area mentioned above, the difference between the maximum and minimum temperature in the same day, especially in winter due to the constant serenity, is sometimes enormous and reaches the lower parts, on the sea, at 19- 20 °. At greater heights these figures are exceeded and the writer has observed in the Jujuy Pune, at 4000 m. high and N. of the tropic, in May, a temperature of −8 ° at dawn and + 38 ° in the shade in the afternoon. This of course in a desert region.
According to Kühn, Argentina can be divided into four climatic regions: the frank subtropical, the temperate subtropical, the temperate, and the Andean region; some of which can be divided into provinces: so that there would be a total of nine climatic provinces.