https://www.weather-atlas.com/en/canada-climate
The climate of Canada
Canada has a mainly cold climate, with short, warm summers and long, frigid winters. The northern and central portions experience a subarctic climate (Köppen climate classification ET, Dfc). The extreme south is mostly humid continental (Köppen Dfa, Dfb), a small portion of which is a cold semi-arid desert (Köppen BSk). The southwestern Pacific coast has an oceanic climate (Köppen Cfb, Cfc). Canada lies in North America and shares a vast border with the United States in the south and Alaska in the northwest. The Pacific Ocean lies in the west, the Arctic in the north, and the Atlantic in the east. The high latitudes, lack of mountains to shield polar air masses, and cold currents are the main factors that influence the climate.
Three oceans together give Canada the longest coastline in the world spread over 151,000 miles. The Labrador current keeps the Atlantic coast colder than the Pacific coast. The landscape is diverse with mountains, plateaus, swamps, and consists of the largest freshwater lakes in the world. The Rocky Mountains block air masses from the west, while the Great Prairies to the east of the mountains have large populations due to warm conditions. Cold air from Siberia, the Siberian Express, brings extreme cold to the northwest. The winter temperatures are below freezing in much of Canada, except for British Columbia in the south. The western slopes of the Rocky Mountains receive up to 2032mm (80") of annual rainfall, and the climate is humid. Chinook winds at the foot of the mountains occasionally raise temperatures in the winter.
The Arctic regions up to Hudson Bay in the north have short summers of three months. Ice and permafrost dominate the Arctic region of Canada. The northwest region, including Yukon, sees warm summers with cool nights. The Great Plains in the Midwest occasionally experience temperatures above 37.8°C (100°F) in the summer. Precipitation is to the tune of 508mm (20") annually, but the plains see violent snowstorms in the winter. The Pacific coast has bright summers, with sea temperatures mild at best. The Great Lakes region in the south receives more than 1016mm (40") of rainfall annually and is prone to heavy snowfall. The east coast is mild and rainy in the summer, with periods of sunny weather. Winters are long, cold, and snowy in the eastern provinces. The mixing of cold and warm currents creates frequent fog near Newfoundland, particularly in the Grand Banks area.
Much of the upper half of Canada has only two seasons. Summers are short and warm, with cool nights. Winters are long and cold, with heavy snowfall and year-round snow cover. The Canadian Prairie is continental, with harsh winters that see temperatures below -40°C (-40°F). The regions in the temperate zone experience all four seasons. The average high temperatures range between 25°C (77°F) to 30°C (86°F) in the southern interior lands. Heat can exceed 40°C (104°F) in the hinterland during the hot season. The east and west coast has daily high temperatures above 21.1°C (70°F) in the summer. The annual rainfall in Canada varies from 508mm (20") in the arid regions to 2032mm (80") in the mountains. The southern temperate regions receive up to 1016mm (40") of rainfall evenly throughout the year. Snowfall is abundant in the north, which receives the least sunshine of fewer than 1500 hours annually. Mount Fidelity in Glacier National Park, in British Columbia, receives 14097mm (555") of snow annually. Snow remains on the ground for more than 250 days in many places. The Great Prairies witness ample annual sunshine of more than 2300 hours.