Cornwall residents are experiencing a brief surge of summer-like heat this week as temperatures climb, though the shift brings a risk of storms and a sharp drop in temperature Wednesday night.
According to Environment Canada, a temperature of 28°C was recorded at the nearby Saint-Anicet station at 5:00 PM on Tuesday, May 19, 2026, with humidity making it feel like 33°C. This warm air, moving north from the United States, is part of a larger weather pattern affecting much of southern Ontario, where heat warnings have been issued as the region sees its first significant heat event of the season. However, no heat warning is currently in effect for the Cornwall area.
While Tuesday remains warm, conditions are expected to shift as the evening progresses. There is a risk of thunderstorms tonight, followed by a transition to cooler weather. By Wednesday, temperatures will reach a high of 22°C, but residents should prepare for a significant cooldown overnight as temperatures are expected to drop to 3°C, bringing a risk of frost.
The remainder of the week offers more settled conditions, with sunshine expected on Thursday and Friday. Daytime highs for those days are forecasted to reach 16°C and 19°C, respectively. The weekend is expected to remain cloudy with a 40 percent chance of showers and daytime highs near 17°C to 18°C.
