Newfoundland has a humid climate with short, cool summers and cold, snowy winters. Because of its position on the eastern side of North America, it comes under the influence of continental air masses and experiences a great range between winter and summer temperatures. Although it lies in the same latitude, its climate is much less equable than that of Vancouver Island. The average July temperatures range from 50°F. to 63°F. but only a very small part of the island has mean July temperatures above 60°F. January mean temperatures range from 10°F. to 26°F. While the winters of the south coast are relatively mild, they are much more severe on the west coast and especially toward the north where they are affected by the cold polar continental air masses. The advent of spring is retarded and summer temperatures, especially on the northeastern coasts, are kept low by the ice laden Labrador current. The frost-free season is relatively short, the average length, in those sections which are considered to have agricultural possibilities, ranging from 108 to 140 days.
The island has abundant precipitation, having the equivalent of 30 to 55 inches of rainfall per annum. In general the amount is least in the northwest and greatest in the southeast, but everywhere there is a fairly uniform distribution from month to month. Snowfall is heavy with only a portion of the south coast receiving less than 80 inches per annum while a belt of heavy snowfall (120 inches per annum) covers the interior and the northeast coast.
The weather of Newfoundland is exceedingly variable being affected by the cyclonic storms which, every few days, leave the continent by way of the Gulf of St. Lawrence. They are more frequent during the winter months often being accompanied by very high winds. Ice storms, or freezing rain, occur when warm air masses from the Atlantic sweep over the frozen land.
The coasts of Newfoundland are foggy, although no more so than the southern coast of Nova Scotia. St. John's has an average of 37 foggy days per year, but the Grand Banks, to the east of the island, are known as one of the foggiest areas in the world. June and July are the foggiest months while there is much less "thick weather" in the winter season. Fogs are caused by the warm moist air from the south mixing with the air which has been chilled by the Labrador current.
Closely related to the climate are the ice conditions of the sea surrounding the island. Early in December sea ice begins to form in the shallow bays of the northern peninsula. It gradually spreads southward during the winter reaching its greatest extent in March when only the south coast is open. Normally ships can reach St. John's through a narrow coastal passage which, however, may be closed when the ice pack is driven on shore by a southeasterly wind. The Strait of Belle Isle is closed to navigation from December until June.
Besides the local ice, there is Arctic ice which drifts southward from Davis Strait. It also reaches its maximum extent in March covering the Grand Banks to latitude 45°. During the spring and summer, icebergs are also observed. They originate from land ice in the far north and usually require about two years to reach the Grand Banks. Because of their great bulk which is mostly underwater, they are very dangerous to navigation. They melt rapidly when they reach the warm waters of the Gulf Stream.
Newfoundland lies within the Boreal Forest region, its short cool damp summers and long cold winters being unsuitable for the growth of most deciduous trees. There is, however, considerable variation in the vegetative pattern. Only two fifths of the area is covered with productive forest while one half is composed of barren lands, bogs and lakes. The chief forest areas lie within the drainage basins of the large rivers, the Humber, the Exploits, the Gander and the Terra Nova. Good timber is also found along the rivers which drain into White Bay and St. Georges Bay.
Elevation and drainage are the principal factors affecting vegetation. The best forest growth is found on well drained slopes which support mixed stands of balsam fir (Abies balsamea), white spruce (Picea glauca), black spruce (P. mariana), white birch (Betula papyrifera) and even some white pine (Pinus strobus). On the forest floor are found pigeon-berry (Cornus canadensis), snake-berry (Clintonia borealis), blueberry (Vaccinium sp.), sheep laurel (Kalmia angustifolia) and feather moss (Hypnum sp.). This plant association characterizes most of the productive forest.
The St. Georges district in the southwest may be considered a small subregion in which the forest is somewhat akin to that of the Acadian region. Here the lower well drained slopes carry more hardwoods including red maple (Acer rubrum) and yellow birch (Betula lutea) as well as white spruce and balsam fir. The undercover may contain trillium (Trillium sp.), violet (Viola sp.) and wood-fern (Aspidium sp.).
In the poorly drained swamp forests of the valley bottoms, black spruce is the dominant tree with an undergrowth of labrador tea (Ledum sp.) and sheep laurel. At higher elevations also black spruce is the dominant tree, giving way on the plateau summits at about 1,200 feet to open barrens of reindeer moss (Cladonia) and lichens, with sometimes small stunted black spruce. Sphagnum bogs may be found in both upland and lowland locations.
Several factors tend to make the soils of Newfoundland a poor base for agriculture except in favoured localities. They are podzols. The humid climate and the coniferous forest cover produce highly leached, acid conditions while the hard old granite rocks have, at best, only a limited supply of the elements needed for plant growth. Only a few small areas have been examined by soil surveyors as yet, but from their reports it is evident that the best chances for agricultural development lie in the coastal plains and the alluvial bottoms of the larger valleys where the soils are deep and less severely weathered. Among the locations which may be mentioned are the upper Humber Valley, the Codroy Valley, the northwest coast, St. Mary's Bay and Grand Falls.