Of the Himalaya is almost rainless, 6 or 8 in.
The greater part is within the almost rainless zone.
The rainfall is very unequally distributed: in the western part, which comes near to the limits of the rainless region of Asia, it is very scanty, and scarcely averages more than 5 in.; in the south-west the fall is more copious, sometimes exceeding 100 in.
North of the apex of the delta and the boundary between the deltaic and inland tracts, the rainfall gradually lessens as far as Minbu, where what was formerly called the rainless zone commences and extends as far as Katha.
The climate is extremely dry, but this is compensated for by the heavy mists which sweep up from the plains during the rainless months and exercise a most beneficial effect in the coffee-growing districts.
Evaporation is naturally greatest in the enclosed seas of the nearly rainless subtropical zone such as the Mediterranean and Red Sea.
In countries nearly rainless, such as Egypt or Sind, there can be no cultivation without irrigation.
This increase was not due to famine in Sind, for that rainless province depends always on the Indus, as Egypt does on the Nile, and where there is no rainfall there can be no drought.
Except a narrow belt on the north along the Mediterranean shore, Egypt lies in an almost rainless area, where the temperature is high by day and sinks quickly at night in consequence of the rapid radiation under the cloudless sky.
This region is rainless, barren and inhospitable, absolutely destitute of vegetation except in some small river valleys where irrigation is possible, and on the slopes of some of the snow-covered peaks where the water from the melting snows nourishes a scanty and coarse vege tation before it disappears in the thirsty sands.
The high altitudes of the Andean region also introduce vertical zones of temperature, modified to some extent by the rainless plateaus of the north, and by the excessive rainfall of the south.
Formerly wheat was grown chiefly in the region of long rainless summers, and the ripened grain was thrown upon uncovered earth floors and threshed by horses driven about over the straw, but this antiquated process was not suited to the climate and enterprise of the more southern provinces, and the modern threshing-machine has been introduced.
Extensive deposits of the salt (called caliche in its crude, impure state) in the provinces of Tacna, Tarapaca, Antofagasta and Atacama owe their existence to the rainless character of the climate.
December, January, February and March are practically rainless; the rains, beginning in April or May, reach their maximum in July, August and September, and rapidly diminish in October and November.
Nevertheless, the west coast north of the Olifants river is practically rainless and there is great difference between day and night temperatures, this part of the coast sharing the characteristics of the interior plateau.
Above sea-level) it ffeezes so hard in December and January that skating is carried on on the sheet of water in the Buen Retiro; and, as winter throughout Spain, except in the maritime provinces of the north and north-west, is the season of greatest atmospheric precipitation, snowfalls are frequent, though the snow seldom lies long except at high elevations, The summers, on the other hand, are not only extremely warm but almost rainless, the sea-winds being deprived of their moisture on the edge of the plateau.
In this zone there prevails a genuine sub-tropical climate, with extremely warm and almost rainless summers and mild winters, the temperature hardly ever sinking below freezing-point.
From the north of Manchuria the Khingan range stretches southward to the Chinese frontier near Peking, east of which the drainage falls into the Amur and the Yellow Sea, while to the west is an almost rainless region, the inclination of which is towards the central area of the continent, Mongolia.
The flora of the rainless region of south-western Asia is continuous with the desert flora of northern and eastern Africa, and extends from the coast of Senegal to the meridian of 75° E., or from Asia.