The climate is particularly temperate, but the extremes of sensible heat and cold are increased by the humidity. The range of the thermometer is from 45° Fahr., the lowest known extreme, or 48°, the ordinary lowest extreme of January, to 82°, the ordinary, or 86°, the highest known extreme of July, near the level of the sea. Between these two points (both taken in the shade) there is from month to month a pretty regular gradation of increase or decrease, amounting to somewhat less than four degrees. In winter the prevailing winds are from the north-west, west and south; in summer the most frequent are the north, north-east and east. The weather is often extremely stormy, and the winds from the west and south-west render the navigation of the coasts very dangerous.


The mammalia of the Azores are limited to the rabbit, weasel, ferret, rat (brown and black), mouse and bat, in addition to domestic animals. The game includes the woodcock, red partridge (introduced in the 16th century), quail and snipe. Owing to the damage inflicted on the crops by the multitude of blackbirds, bullfinches, chaffinches and green canaries, a reward was formerly paid for the destruction of birds in St Michael's, and it is said that over 400,000 were destroyed in several successive years between 1875 and 1885. There are valuable fisheries of tunny, mullet and bonito. The porpoise, dolphin and whale are also common. Whale-fishing is a profitable industry, with its headquarters at Fayal, whence the sperm-oil is exported. Eels are found in the rivers. The only indigenous reptile is the lizard. Fresh-water molluscs are unknown, and near the coast the marine fauna is not rich; but terrestrial molluscs abound, several species being peculiar to the Azores.


The general character of the flora is decidedly European, no fewer than 400 out of the 478 species generally considered as indigenous belonging likewise to that continent, while only four are found in America, and forty are peculiar to the archipelago. Vegetation in most of the islands is remarkably rich, especially in grasses, mosses, and ferns, heath, juniper, and a variety of shrubs. Of tall-growing trees there was, till the 19th century, an almost total lack; but the Bordeaux pine, European poplar, African palm-tree, Australian eucalyptus, chestnut, tulip-tree, elm, oak, and many others, were then successfully introduced. The orange, apricot, banana, lemon, citron, Japanese medlar, and pomegranate are the common fruits, and various other varieties are more or less cultivated. At one time much attention was given to the growing of sugar-cane, but it has now for the most part been abandoned. The culture of indigo, introduced in the 16th century, also belongs to the past. A kind of fern (Dicksonia culcita), called by the natives cabellinho, furnishes a silky material for the stuffing of mattresses and is exported to Brazil and Portugal.


The inhabitants of the islands are mostly of Portuguese origin, with a well-marked strain of Moorish and Flemish blood. There is a high birth-rate and a low average of infant mortality. A large proportion of the poorer classes, especially among the older men and women, are totally illiterate, but education tends to spread more rapidly than in Portugal itself, owing to the custom of sending children to the United States, where they are taught in the state schools. Negroes, mulattoes, English, Scottish and Irish immigrants are present in considerable numbers, especially in Fayal and St Michael's. The total number of resident foreigners in 1900 was 1490.