The distribution of rainfall, so important for vegetation and animal life, is fairly uniform in Southern Quebec where the mean annual precipitation ranges between 35 and 40 inches. It decreases to 30 inches westward and to 20 and even 15 inches in Northern Quebec. In the Laurentide Park, the summits receive as much as 55 inches, but are closely surrounded by isohyets of 50 and 45 inches; the latter one expands far south of the massif, and joins the Appalachian heights in the Eastern Townships. Away from this centre precipitation decreases in two opposite directions: eastward the shores of the Estuary and the Gulf are below 35 inches from Rivière du Loup and Tadoussac to Gaspé; westward, the upper Ottawa Valley is even below 30 inches. On one hand cold waters seldom produce rain while on the other the decrease towards the interior is to be explained by the more continental type of weather. The heavier precipitation between is produced not only by higher altitudes north of Quebec City, but by the fact that in summer the warm air masses from the south collide here with the colder masses of the north.
Quebec has the heaviest snowfall in Eastern Canada. At 19 stations out of 49 where the snowfall is recorded and published, 1 the depth of the snow is over 100 inches. Montreal and Quebec have 112 and 123 respectively. Few stations have less than 80 inches. The many ways in which the snow cover is beneficial to the land are well-known. Snow is not only welcomed by sportsmen but by foresters and farmers. It protects the roots of the plants and affords easier ways of transport even for truck driving in the bush. Water from the melting snow also adds moisture to the soil in springtime.
A further idea of climatic conditions is obtained when we consider the number of precipitation days and the hours of sunshine. Montreal and Quebec are only 160 miles apart and they both have about 40 inches of precipitation. But, for a period of ten years, Montreal averaged 164 days per year with measurable precipitation while Quebec had 174 days. Montreal had 1803 hours of sunshine while Quebec had 1745 hours per year. Continental climates are characterized by short periods of precipitation, even though it may be relatively abundant. On the other hand, Maritime climates have fine persistent rain even though the total amount is less. In this respect then, Montreal has a more continental climate than Quebec.
Winds and Weather
In the St. Lawrence Valley prevailing winds are from the northwest in Winter and from the southwest in Summer. They are usually accompanied by fine weather. In the Gulf and the Estuary northeast winds bring bad weather in Summer. Winter winds from the south and southeast are likely to raise the temperature, but they often bring snow storms followed by thawing. In any case, Southern Quebec enjoys the kind of weather to which it is entitled by latitude.
Based upon consistent differences in the average climatic statistics, nine climatic subdivisions may be recognized in Southern Quebec. They are: the Appalachians, the Gaspé Uplands, the St. Lawrence Lowlands, the Estuary of the St. Lawrence, the Gulf of St. Lawrence, the Laurentians, the Lake St. John Area, Western Quebec and Eastern Quebec. The large cold area of Northern Quebec may be regarded as a tenth climatic subdivision.
Particularly noticeable is the variation in precipitation regimes. Precipitation is adequately distributed over the year at all southern stations but in the north there is a tendency for the early spring to have less and the late summer months to have more moisture than the average.