During the monsoon the climate is very damp, and at times even cold and raw, thick clouds and mist enveloping the sky for many days together.
In winter, for example, when the northern monsoon begins to blow, numbers of denizens of the Sea of Okhotsk swim southward to the more genial waters of north Japan; and in summer the Indian Ocean and the Malayan archipelago send to her southern coasts a crowd of emigrants which turn homeward again at the approach of winter.
At Ajmer, an old meteorological station at the eastern foot of the range, the wind is predominantly south-west, and there and at Mount Abu the south-west monsoon rains are a regularly recurrent phenomenon, - which can hardly be said of the region of scanty and uncertain rainfall that extends from the western foot of the range and merges in the Bikaner desert.
It is to be noted that the climate of the islands of the Pacific becomes more and more healthy the farther they are from the monsoon region.
In the monsoon region, where the barometer rises o 38 in.
The south-westerly winds which prevail north of the equator during the hot half of the year, to which navigators have given the name of the south-west monsoon (the latter word being a corruption of the Indian name for season), arise from the great diminution of atmospheric pressure over Asia, which begins to be strongly marked with the great rise of temperature in April and May, and the simultaneous relatively higher pressure over the equator and the regions south of it.
The flora of Siberia presents very great local varieties, not only on account of the diversity of physical characteristics, but also in consequence of the intrusion of new species from the neighbouring regions, as widely different as the arctic littoral, the arid steppes of Central Asia, and the wet monsoon regions of the Pacific littoral.
Its mountains are insufficient in elevation and extent to attract their full share of the monsoon rains, which fall so abundantly on the Abyssinian highlands on the other side of the Red Sea; for this reason Arabia has neither lakes nor forests to control the water-supply and prevent its too rapid dissipation, and the rivers are mere torrent beds sweeping down occasionally in heavy floods, but otherwise dry.
In Annam the rainy season begins during September and lasts for three or four months, corresponding with the northeast monsoon and also with a period of typhoons.
The full force of the monsoon is, however, broken by the western frontier hills; and while the rainfall at Mergui is over 180, and at Moulmein 240 in., that of Bangkok seldom exceeds 54, and Chiengmai records an average of about 42 in.