Sizzling start: Heat and humidity to grip Toronto and southern Ontario this week
Posted June 17, 2025 7:32 am.
Last Updated June 17, 2025 7:45 am.
Summer is set to make a strong entrance in Toronto and across southern Ontario, with a prolonged spell of hot and humid weather expected this week.
Daytime highs are forecast to climb into the upper 20s and low 30s in parts of the region by Sunday, with humidity making it feel even warmer. In Toronto, residents can expect more than an entire week of daytime temperatures reaching at least 25 °C, possibly 30 °C on Wednesday.
Summer officially arrives on Friday at 10:42 p.m. ET.
So far this year, 30-degree days have been few and far between. Toronto has only seen one such day—June 4—and hasn’t experienced more than two consecutive days above 25 °C since last September.
The rise in daytime temperatures also means increased humidity, which could lead to showers and potential thunderstorms in Toronto and the GTA this week.
Toronto could be headed for scorcher next week
For Wednesday, there is a 40 per cent chance of showers in the afternoon with the risk of a thunderstorm. The potential for rain will increase to 60 per cent in Toronto on Wednesday evening, with a low of 18 °C.
Thursday is shaping up to be a washout in Toronto as Environment Canada forecasts a 60 per cent chance of showers throughout the day and a high of 25 °C. It will cool down by Thursday evening with a forecasted low of 14 °C and a 30 per cent chance of rain.
Looking further ahead to next week, the extended forecast is shaping up to be a scorcher. Though subject to change, Toronto could be headed for humidex values in the 40s on Monday, with sunny skies and a possible daytime high of 33 °C.
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