Warm, humid air mass fuels a thunderstorm risk in southern Ontario
The conclusion to the weekend could be stormy in parts of southern Ontario as humidity and warmth rise in the region, making for a summer-like day for some areas
The warmest day of the year for parts of southern Ontario is likely as mild, humid air spreads into the region.
In fact, Sarnia, Ont., already experienced its warmest day of the year on Saturday, and in Canada, actually. It scored the warmest temperature for 2024 so far with a reading of 26.8°C. Temperatures are expected to soar into the 20s again for many locales on Sunday, with humidex values reaching into the mid- and upper 20s.
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However, with that comes a renewed risk for thunderstorms on Sunday, similar to on Saturday, but won't be as potent. Any that form should remain non-severe in nature. Saturday saw a number of severe storms push through parts of Georgian Bay and into northeastern Ontario. Photos of large hail surfaced on X.
The mild temperatures should be lingering on Monday, but there is uncertainty in how warm they will get, so they could be a tad lower than what they are expected to reach on Sunday.
Early-summer tease again on Sunday
On Saturday, Sarnia, Ont., saw its warmest day of the year so far, also enough to make it the hottest temperature in Canada to date in 2024. It scored a balmy reading of 26.8°C.
Prior to that, the warmest readings we’ve seen so far this year include:
26.1°C in Windsor on April 14
23.8°C in Hamilton on April 9
20.6°C in Toronto on March 13
19.9°C in London on April 14
Daytime highs on Sunday will soar into the mid-20s for many communities, with humidex values possibly reaching into the high 20s.
Given the warmth in the forecast, Toronto and London are on track to beat 2024’s high-mercury mark by Sunday, while Hamilton might fall short by just a hair.
Enough instability could build that we may have to contend with more thunderstorms during the second half of the day.
We’ll see a renewed risk for showers and thunderstorms over southern Ontario during the day Sunday as this warm and unstable air builds in.
This includes much of the Highway 401 corridor from Windsor to Kingston, including Toronto, as well as north toward Bancroft and Barrie. Look out for heavy rain and gusty winds in any of the feistier storms that bubble up on Sunday.
Warmth sticks around into early this week
Another rainy system tracking into northern and central Ontario on Monday will keep the unseasonably warm air parked over the southern half of the province to start the week. However, there’s uncertainty in just how warm things will get on Monday, so it could end up being slighly cooler than on Sunday. We could see big temperature variations over short distances with clouds and lake breezes.
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We’ll see additional showers in southern Ontario late Monday afternoon and into the evening.
Temperatures will likely start to moderate back toward seasonal as we head into the second half of this week. Warm-weather lovers may not have to wait long for above-seasonal conditions to return, as more unseasonable warmth could arrive in time for the beginning of May.
Stay with The Weather Network for all the latest on your forecast across Ontario.
