Why do the interior plains of Canada have very cold winters and hot summers?

The interior plains of Canada experience a continental climate characterized by very cold winters and hot summers primarily due to the effect of continentality.12

Because these regions are located far from the moderating influence of large bodies of water, they lack the temperature-stabilizing effects that oceans provide. Water has a much higher heat capacity than land, meaning it warms and cools slowly, whereas land surfaces—which have low heat capacities and reduced evaporation rates—respond rapidly to solar radiation and atmospheric conditions.34

The temperature extremes are further influenced by the movement of distinct air masses:

• Winter: The region is dominated by cold, dry polar continental air masses that form over the Canadian Shield, bringing subzero temperatures and stable, cold air.5
• Summer: As the heart of the continent heats up, the region is influenced by warm, unstable air masses, including tropical continental air, which can lead to extremely hot, droughtlike conditions.5

Consequently, interior locations exhibit a much wider daily and seasonal temperature range compared to coastal areas.34