Climate. – The climate of Iceland, relative to its latitude, is very mild. The average annual temperature on the southern and western coasts fluctuates between 3 ° and 4 °, in winter between 0 ° and −2 °, in summer between 9 ° and 10 °. On the northern and eastern coasts, the average annual temperature ranges between 1 ° and 2 °, in winter between −2 ° and −4 ° and in summer between 6 ° and 7 °. The interior, however, has a very rigorous continental climate due to its elevation above sea level.
Incosta weather and storms are very frequent, especially on the east coast. The annual rainfall is 870 mm in Reykjavik, 650 mm in Stykkisholm (on Snaefelesnes), 277 mm in Grimsey, 1180 mm in Beru fjördur (on the eastern coasts). The highest annual rainfall is recorded in Vik (2175 mm.) On the southern shores of Mýrdals jökull. In winter, snow is rather scarce in the southern part, and abundant, instead, in the northern part of the island. It should be noted that many parts of the coasts are often blocked by floating ice and therefore the summer season is completely missing.
Iceland has many lakes, the largest of which is Thingvallavatn (120 sq. Km., Depth 116 m.); followed, in order of size, by the Thórisvatn west of the Vatna jökull, the Mývatn in the northern part of the island, the shallow Hvitárvatn right on the Lang jökull, and the two groups of lakes, the Fiskivötn to the west of the inner mountainous region, and the Veidivötn south of Thórisvatn. The deepest lake is Öskjuvatn, a crater lake on Askja (about 350 m deep).
Rivers are numerous and rich in water in southern Iceland; for the most part they descend impetuously and form several waterfalls. In general they are so shallow that they can be waded, but during spring floods and volcanic eruptions (which produce sudden melting of ice and snow) they swell enormously and their floods have devastated extensive regions in many places. Among the rivers of southern Iceland we must remember the Skaptá the Kúdafljót, the Markarfljót, which forms the delta called Landeyjar, the Thjórsá, the longest river in Iceland (210 km.) And richest in water (on average 415 mc. to the second), with the tributary Tungnaá, the Ölfusá-Hvita, with the tributary Sog, which is the emissary of Lake Thingvallavatn. The waterways of western Iceland are small, with the exception of the Hvitá, which flows into the Borgar fjördur; among the most notable rivers of northern Iceland are the Blanda, which flows into the Hunaflói, the Heradsvötn, the Eyjafjardará, which ends with a beautiful delta in the Eyja fjördur, the Skjálfandafljót and the Laxá, which originates from Lake Mývatn and throws himself into the Skjálfandi fjördur; finally the Jökulsá, the longest river in northern Iceland, which flows into the Axar fjördur.
In eastern Iceland flow: the Jökulsá, which has its sources in Heradsflói, and the Lagarfljót, which forms a narrow and deep lake about halfway along its course. On the edge of the plateaus, rivers often form beautiful waterfalls: thus the Thjorsárdal forms the 120m high Háifoss waterfall; the Fljótsdal, the Hengifoss, 115 m high; the Skógá, the Skógafoss, magnificent, more than 60 m high.
Flora and vegetation. – Icelandic flora is intermediate between the arctic flora of Greenland, the arctic flora of northern Europe and the flora of central Europe, the Baltic region: so much so that it has been debated whether Iceland should be phytogeographically linked to northern Europe or to the arctic regions. But in reality it has climatic characteristics of the two regions, independent of its geographical position above the polar circle.
Its flora of vascular plants includes 435 species (phanerogams and vascular cryptogams): in the southern lowlands three quarters of the vascular plants are represented by species of the plains of northern and central Europe, while the highlands and the northern coast have two thirds of arctic plants, many of which from the far north: most of these plants are found in Scandinavia. The areas where the temperature is mild have the same birch (Betula pubescens var. Carpathica) that grows in northern Europe and in other times this tree was much more widespread: but it is over a thousand years that the great birch forests that covered part of the island were cut down for the construction of houses and ships: but still in the middle of the century XVIII trees were seen taller than 12 m. Woody plants generally do not reach great heights: 8-9 m individuals have been found of Sorbus aucuparia. and the specimens of Salix phyllicifolia do not exceed 3 m. The only fruits found on the island are raspberries and blueberries.
Fauna. – The Icelandic fauna, although the island is located near the Arctic Circle and in considerable proximity to Greenland, still shows characteristics of European fauna. Among the mammals found in Iceland we can see the arctic dog (C. Lagopus), the polar bear as occasional guest, some seals living along the coast and a mouse, the Mus islandicus. Birds are of greater interest. About a hundred species have been observed there, some of which are peculiar (Troglodytes borealis, Falco islandicus, Lagopus islandorum, etc.), while the others are species that visit Europe and live in Iceland, or European species also observed on the island. Some other Icelandic resident species (Clangula islandica and Histrionicus torquatus) visit North America. Reptiles and Amphibians are absent and freshwater fishes are absent, with some exceptions (some species of Gasterosteids). Terrestrial molluscs are fairly represented with species belonging to the families of Helicidae, Stenogyridae, Limneidae, Pupidae, etc.
Among the Insects we notice some species of Lepidoptera of the families Geometridi and Noctuidi, of Coleopteri (Carabidi, Cicindelidi, Lamellicorni, Coccinellidi, Curculionidi), various Hymenoptera, Tricotteri and Ditteri sirfidi and culicidi.