Why is there a heavier population disturbance in southern Saskatchewan then northern Saskatchewan?

Canada has ten province and three territories namely: Provinces: Quebec; Ontario; Nova Scotia; New Brunswick; Alberta; Saskatchewan Manitoba; Prince Edward Island; British Columbia and Newfoundland (which includes Labrador that is physically located within its neighboring province of Quebec). Territories: Northwest Territories; Yukon and Nunavut. Approximately 80% of Canada's population (including Saskatchewan) lives in its southern portion which is within 100 miles (161 km) of its only foreign border which is the United States. Most Canadians live in the southern portion of Canada due to its warmer climate.