Winters in Markham are harsh, with temperatures frequently dropping below -20°C and averaging around -4°C to -7°C from January to March. Spring brings a slow warming trend, with temperatures rising to as high as 24°C by April, but still experiencing chilly mornings. Summer is warm and stable, with temperatures consistently ranging between 19-21°C from June to August. Autumn sees a gradual cooling down, with temperatures fluctuating between 3-16°C from September to November. December brings a return of cold winter conditions, with temperatures averaging around 0°C.