The water temperature of the Niagara River fluctuates dramatically with the seasons, as it is fed by the deep waters of Lake Erie. In the peak of winter (February), the water is near freezing, typically between 1°C and 3°C (34°F–37°F), often with significant ice floes moving toward the falls. As spring arrives, it warms slowly, reaching about 10°C (50°F) in May. By the height of summer in August, the surface temperature can reach a surprisingly pleasant 18°C to 24°C (64°F–75°F). In 2026, if you are taking a "Maid of the Mist" or "Journey Behind the Falls" tour, expect the water to feel bracingly cold even in the summer due to the mist and wind. For safety, swimming in the Niagara River is strictly prohibited in most areas due to the extremely powerful and unpredictable currents, regardless of how inviting the temperature might look from the shore.