The Victoria Day long weekend, or the "unofficial kickoff' to summer as some call it, in southern Ontario will be mostly marked by hot, humid and dry conditions. There will be sporadic chances for passing showers and thunderstorms Saturday and Sunday, but many areas won't see any precipitation at all, something that is much-needed to overcome the increasingly dry conditions. Sunday will see a greater chance for thunderstorms, however, thanks to a cold front sinking south, but again, most areas won't see any rain. The front will bring an end to the hot air mass for Monday, as drier, cooler air moves in. More on the timing of these storms and how cool things get for the end of the long weekend, below.
SATURDAY: HOT AND HUMID CONDITIONS PERSIST, SOME STORM RISK
Southern Ontario will continue to feel the summer heat and humidity Saturday, with widespread daytime highs into the mid-20s, even potentially hitting the 30-degree mark in southwestern sections.
Those looking for relief at night won't get much as overnight low temperatures will also hover near 20°C, making for very uncomfortable conditions over the next couple of days. Saturday's humidex values will be closer to the mid-30s for much of southern Ontario.
There will be scattered pop-up showers within the warm sector throughout the day across southern and central Ontario. With the help of the humid air mass in place and daytime heating, there is a non-severe thunderstorm risk, as well. Not a washout of the day by any means, as most areas won't see any rain.
The best opportunity for thunderstorms are most likely in the far northwestern sections, where there's a chance some isolated storms in the afternoon may reach severe levels. There main hazards are heavy rain, large hail and damaging wind gusts.
SUNDAY AND MONDAY: COLD FRONT SINKS SOUTH, HUMIDITY EASES AND HIGHER RISK FOR THUNDERSTORMS
A cold front is expected to slowly sink south through the region on Sunday, with a wide range in temperatures expected and an increased potential for scattred showers and possible thunderstorms.
Due to the early timing of the front, dynamics are not favourable to see much in the way of thunderstorms for southern Ontario until it slices through the southwestern sections by the afternoon hours. Because the front will be fairly moisture-starved, many areas across southern Ontario will remain rain-free, avoiding the growing need for the precipitation.
Temperatures are expected to fall through the day, back down to seasonal or even slightly cooler values for northeast sections first, and likely cottage country by the afternoon hours.
Much of the Golden Horseshoe will squeeze out another summer-like day with temperatures in the upper 20s or low 30s since the cold front holds off until later in the day.
By Victoria Day Monday, cooler weather will return for southern Ontario. In fact, temperatures may drop by 9-11 degrees in the GTA, thanks to an east wind off of Lake Ontario knocking temperatures even a few degrees below normal for some.
LOOK AHEAD: FLIP-FLOPPING TEMPERATURES, WITH COOLER START TO JUNE
Changeable temperatures are expected for the final full week of May, with summer-like warmth returning for Tuesday and Wednesday, which may also feature showers and thunderstorms, turning cooler late week and then warming back up again in time for the weekend with the chance of summer-like warmth for parts of the region.
This changeable pattern, however, has the potential to bring much-needed rain to the region.
A preliminary look ahead to the first week of June shows a period of cooler weather, so the start of meteorological summer could feel more like spring.
Be sure to check back for the latest updates on the weather in Ontario through the May long weekend.