Thunder Bay, Ontario – Monday, September 1, 2025 – Thunder Bay is kicking off September in true dramatic fashion: thick fog, sticky humidity, and a Special Weather Statement warning of potentially heavy rain from slow-moving thunderstorms. It’s a weather cocktail that might require both rain boots and patience today.
As of 7:33 AM, the temperature sits at a muggy 14.9°C, with 100% humidity and visibility reduced to just 0.6 km thanks to dense fog blanketing the region. Winds are light from the west-southwest at 6 km/h, but will strengthen to 20 km/h from the west later this morning. Barometric pressure is 102.3 kPa and rising, suggesting a temporary stabilizing trend—before the afternoon chaos, that is.
Special Weather Statement – Thunderstorms with a Twist
Environment Canada has issued a Special Weather Statement for the City of Thunder Bay, warning of localized rainfall totals between 40 and 60 mm due to slow-moving thunderstorms. While not every neighbourhood will get drenched, those directly under the storm track could see intense downpours and localized flooding concerns. A classic case of “hit or miss,” but if you’re hit—you’ll know it.
Today’s forecast calls for mainly cloudy skies, a 70% chance of showers, and a risk of thunderstorms. Fog patches should burn off late this morning, allowing daytime heating to fuel those potential storms. The temperature will rise to 26°C, with a humidex of 32. The UV index is moderate at 5, so if the sun peeks through, it’s still got a bit of bite.
Tonight and the Days Ahead – Showers Stick Around
Tonight brings partly cloudy skies, but there’s still a 40% chance of showers in the evening, again with a risk of thunder before things calm. Expect fog patches to return overnight, with a low of 11°C.
Tuesday, September 2nd, starts out sunny with increasing cloudiness by noon and a 60% chance of showers late in the day, plus—you guessed it—another risk of a thunderstorm. Fog in the morning should lift quickly, and the day warms to 25°C, feeling like 29°C with the humidex. Winds will shift dramatically—first from the south at 20 km/h, then switching to a brisk northwest at 30 km/h by late afternoon.
Tuesday night remains cloudy with a 60% chance of rain, and temperatures dip again to 11°C.
Looking ahead to Wednesday, we stay cloudy with a 60% chance of more showers and a much cooler high of 14°C. Overnight temperatures fall to +5°C, and Thursday continues the cool-down with a high of 11°C and a 40% chance of light showers.
Atmospheric Stats & Weather History
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Current Temperature: 14.9°C
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Wind: WSW at 6 km/h, becoming W 20 km/h later
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Pressure: 102.3 kPa, rising
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Humidity: 100%
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Visibility: 0.6 km
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Historic High for Sept 1: 29.7°C (1983)
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Historic Low for Sept 1: 1.6°C (1976)
What to Wear in Thunder Bay Today?
Start with layers and waterproof gear. A light rain jacket or umbrella will be handy, especially this afternoon. With the humidex soaring into the 30s, stick to breathable fabrics to avoid feeling like you’re wearing a personal greenhouse. Keep a dry change of clothes on standby if you’re out during the storm window.
Weather Trivia – Why Thunder Bay Lives Up to Its Name
Despite its name, Thunder Bay doesn’t top the charts for thunderstorm frequency in Ontario. But thanks to its proximity to Lake Superior, the city often sees localized convective storms during late summer and early fall, especially when humid air and lake breeze boundaries collide. It’s a thunderous name that occasionally lives up to the hype.
