Environment Canada has issued a heat warning for southern Ontario, including Toronto, which is currently experiencing its third heat wave of the summer. The heat warning is expected to last until Thursday, bringing hot and muggy conditions to the region. This weather pattern is associated with a tumbling ridge that is ushering in warm air. Alongside the heat, there is an increased risk of severe thunderstorms across southern Ontario and parts of Quebec through the weekend and into the following days. These storms could produce heavy downpours, large hail, strong winds, and even funnel clouds. A low-pressure system moving into Ontario starting Friday is expected to intensify the thunderstorm threat through Sunday. The Prairies and northwestern Ontario are also under a risk for large hail, strong winds, and funnel clouds as severe storms move eastward. Residents are advised to plan for the possibility of multi-day storms amid the ongoing heat wave conditions.