The tornado warnings that were previously issued in southern Ontario have now ended, however, the risk for severe weather continues. The heat and humidity will bring temperatures back to the 30-degree mark in some parts of the region, including the GTA. This could also help spark thunderstorms in the afternoon that could become severe in southwestern regions. Much cooler air will remain in the eastern areas, with daytime highs hovering around or below 20°C. Friday will see the severe storm threat linger in the southwest, with more widespread rain and storms in the overnight hours. A closer look, below.
- Potential severe storms in southwestern Ontario Thursday afternoon
- Oppressive heat and humidity for most of the south Thursday
- More stormy weather Friday, ahead of a weekend cooldown
- Keep on top of severe weather ALERTS in your area
THURSDAY: HEAT, HUMIDITY INCREASES, SEVERE STORMS POSSIBLE
A boundary draped across the province will continue moving south Thursday and may spark severe thunderstorms in the southwest, with the aid of lake breezes and the heat and humidity. While the storm potential will be more widespread, areas in the southwest will be at greatest risk for seeing them reach severe criteria.
After the line of morning storms move out in the south, more are expected to redevelop in the afternoon and evening. Any severe storms that spark may bring strong wind gusts, heavy rainfall and small hail. Storms may continue overnight, lasting into early Friday morning.
Temperatures will be near or at the 30-degree mark in parts of the south, while the southwest will hit the low 30s, though they will feel like 40 in Windsor. The sharp contrast in temperatures will continue, however, as cooler air will remain in place over eastern and cottage country areas, where daytime highs will be stuck in the upper teens and low 20s.
FRIDAY: ROUNDS OF STORMS, HEAVY RAINS
The boundary will continue to track south Friday, fuelling the potential for severe thunderstorms Friday afternoon and evening, but will be confined to the southwestern areas. While there is a risk for non-severe storms in the south, most areas will be rain-free.
However, the boundary will then lift northwards Friday night, bringing in widespread rain and thunderstorms into the overnight hours, lingering into early Saturday morning, in southern, eastern and central Ontario.
The system will tap into Gulf of Mexico moisture associated with the remnants of Laura, so parts of southern Ontario could see 30-50 mm of rain through Saturday.
Temperatures will be slightly cooler, but still muggy, with humidex values in the low- to mid-30s in the south. Daytime highs will be cooler in the eastern and cottage country areas, with temperatures in the low 20s, with more comfortable humidity levels.
LOOK AHEAD: WEEKEND COOLDOWN, BUT TEMPERATURES TO REBOUND BRIEFLY
Following the passage of the system, cooler temperatures and gusty winds will move in, along with lake-enhanced showers Saturday night and Sunday morning. Conditions will be fair and cool for the start of next week, but then a warming trend is expected by mid-week.
There is also the potential for a brief return to very warm and humid conditions late week, but then becoming more unsettled as a cold front approaches, with a system or two possible along the boundary. At this point it looks like cooler weather will return during the Labour Day weekend.
Keep an eye on the forecast as we continue to monitor Ontario's weather outlook.