Midweek Forecast: Humidex Highs and Stormy Skies on Deck
June 18, 2025 – A Steamy Start with Showers in the Forecast
TORONTO – If you’re stepping out this morning and already feeling sticky, you’re not imagining it. Toronto’s day begins at a warm and muggy 22°C, with a Humidex reading of 29 – and it’s only going up from here. It’s a classic humid Southern Ontario day that could end with rumbles of thunder and a splash of rain, so be sure your umbrella isn’t hiding in the back of the closet.
As of 6:00 AM EDT, conditions at Toronto Pearson International Airport report mostly cloudy skies, pressure rising at 100.9 kPa, and humidity at a tropical 88%. The dew point sits at 19.7°C, and winds are calm from the north at just 3 km/h, creating an almost still, steamy start to the day. Visibility is good at 19 km, but it may get a bit hazy as the air thickens through the day.
Today: Heat and Humidity Building Toward Thunderstorms
The forecast calls for mainly cloudy skies with a 40% chance of showers developing this afternoon — and the risk of a thunderstorm is definitely on the radar. Temperatures will rise to 28°C, but it’ll feel more like 37°C with the Humidex, so stay hydrated and take it easy if you’re outdoors. The UV index is 8, which is very high, so sunscreen is a must if the sun peeks through the cloud cover.
Tonight: Storms Possible, Winds Pick Up
Clouds will stick around into the evening with a 60% chance of showers and the potential for more thunderstorms. Winds will shift and become southerly at 20 km/h, nudging temperatures to an overnight low of 19°C. It’s going to be another muggy night — one of those open-window evenings where you might want to keep a fan on standby… just in case Mother Nature decides to provide her own light show.
The Outlook: Breezy Thursday, Sunny Friday
Thursday, June 19 brings clouds and a 30% chance of morning showers, with winds shifting dramatically from southwest to north at 30 km/h by the afternoon. Expect a high of 24°C with a Humidex of 29, and interestingly, a UV index of just 1 — so it might be a good indoor day if the breeze makes it feel cooler.
Friday, June 20 is shaping up beautifully with sunny skies and a high of 26°C, before a slightly unsettled Saturday with a high of 28°C and a 40% chance of evening showers.
Wardrobe Suggestion
Break out the light, breathable fabrics today — think linen shirts and moisture-wicking tops. A compact umbrella or light rain jacket might come in handy later in the day. And don’t skip your sunscreen, even if clouds are hanging around — the UV index is still punching above its weight.
Toronto Weather Trivia
Did you know that Toronto’s highest ever June temperature was a scorching 38.3°C, recorded back in 1949? Thankfully, we’re not flirting with that today — but when the Humidex climbs into the 30s, it certainly feels like we are. Toronto’s humid summer air is often referred to as “sticky weather” for a reason — and it’s thanks to our proximity to Lake Ontario, which keeps things moist even when skies stay dry.
