There'll be no letup in this extreme heat Sunday, with daytime highs once again hitting the low 30s and humidex values in the upper 30s, possibly hitting the low 40s for some. This kind of humidity is a good cauldron for thunderstorms, and Sunday's greatest chance will be in the northwest, where one or two tornadoes will be possible. In the south, most severe risk looks to stay in Quebec, but that may change as the afternoon nears. For a more detailed look, read on.
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SUNDAY: SEVERE STORM THREAT IN MULTIPLE REGIONS AS HEAT CONTINUES, TORNADO RISK IN THE NORTH
Sunday will offer little relief from the oppressive heat beneath the high pressure that's draped over the province, with temperatures once again soaring into the lower 30s. Humidex values will make it feel more like the mid-to-upper 30s in most places, and perhaps even the low 40s in a few spots.
There will also be a high risk for severe thunderstorms in northwestern Ontario Sunday afternoon and evening, also carrying the potential for supercells and one or two tornadoes. The threats also include large hail, strong wind gusts and heavy rain. Most storms that do form in the region will be severe in nature.
As well, the system tracking in the northern areas will allow much of southern and central Ontario to once again remain in the warm sector. There will be plenty of daytime heating and instability building will allow for possible lake-breeze boundaries to form in these regions.
In terms of storm threat, that's been shifting as the forecast tightens up, but as of Saturday evening, the south's Sunday severe risk showed signs of staying over the border in Quebec, but people in the region should be prepared for that to change Sunday.
Should any severe storms pop up in eastern Ontario, the main threats will be large hail, strong winds, and heavy rainfall.
EARLIEST JUNE HEAT WAVE ON RECORD?
Depending on how long it lasts, this stretch of extended heat could be one of the earliest on record for June.
The last time the city of Toronto for example, saw five days of 30°C+ temperatures in June was back in 1949 from June 11-15. There was however, an even longer seven day stretch of extreme heat as early as May 14 in 1962.
Regardless, these sizzling temperatures so early in June will likely be record-setting and will help to tip the month as a whole to the above seasonal side.
Some relief from the heat and humidity will come at the end of next week and weekend, as a cold front crosses the region and brings temperatures closer to seasonal, with much lower humidity in behind the system.
Precipitation-wise, widespread thunderstorms are expected mid-week as a cold front sags south through the region, but still uncertainty on the timing of the front.
Stay tuned to The Weather Network for the latest on the incoming heat in Ontario.