Humid Air Lingers as Fog Fades and Sunshine Breaks Through
THUNDER BAY – WEATHER – If you stepped outside this morning and felt like you were walking into a damp sponge—you’re not wrong. Thunder Bay is off to a foggy and humid start, but hang tight: brighter skies and warmer air are on the way. It’s a classic September shuffle, and the weekend will give us a little bit of everything—fog, sunshine, clouds, and yes, a touch of summer-style warmth.
Fog and Full Humidity Start the Day
As of 7:00 AM EDT, skies over Thunder Bay Airport are cloudy, with the temperature sitting at a muggy 14.0°C. With a dew point of 14.0°C and humidity at 100%, the air is completely saturated—basically, it’s the kind of morning that curls your hair and fogs up your glasses. Visibility sits at 19 km, not too bad thanks to a light easterly breeze at 4 km/h. The barometric pressure is 101.8 kPa and falling, signalling that today’s calm start might bring some shifts ahead.
Fog patches will dissipate later this morning, and skies will become a mix of sun and cloud this afternoon. The high will climb to 23°C, but with the moisture still hanging in the air, it’ll feel closer to 29°C with the humidex. The UV index is 5, a moderate level, so sun protection is still advised if you’re spending time outdoors.
For the history buffs: Thunder Bay’s record high for September 13 is 27.4°C, while the record low dipped to 1.8°C. Today’s forecast is warm and humid, sitting closer to that upper range—proof that summer’s not quite done with us yet.
Tonight: Clear to Cloudy with More Fog Rolling In
Tonight, skies will start out clear, becoming partly cloudy late this evening, and yes—fog patches will return overnight. It’ll be another night of high moisture and mild temperatures, with a low of 12°C.
Sunday: Cloudy Start, Clearing Later
Sunday, September 14, begins cloudy with fog patches, but similar to Saturday, those foggy conditions will dissipate in the morning, giving way to a mix of sun and cloud. Cooler than today, the high will reach 18°C, but the UV index will bump up to 6, so be sure to lather on that SPF if you’re heading out after the fog clears.
Sunday night stays cloudy, with another low of 12°C—a gentle night that continues this mild September trend.
Monday Forecast: Cloudy But Warm
Monday, September 15, brings cloudy skies throughout the day, but the warmth returns with a high of 23°C. No rain in the forecast—just a grey blanket overhead. Monday night remains cloudy with a low of 14°C, staying mild and calm.
What to Wear?
Today’s the perfect excuse for breathable clothes with layers. It may feel cooler in the morning mist but will warm up quickly by afternoon. Keep a light jacket handy for early fog and cooler evening hours, and don’t forget the sunglasses when the sun finally peeks through.
Weather Trivia: Thunder Bay’s Fog Factory
Thunder Bay experiences fog more frequently than many might think—especially in September. That’s because cool overnight land temperatures mix with warm, moisture-rich air from Lake Superior, creating ideal conditions for radiation fog. It’s common to wake up in a dense fog that vanishes as soon as the sun starts heating the ground.
META Description:
Thunder Bay starts foggy and humid with a high of 23°C and humidex of 29. Fog clears by midday. Cooler, cloudy Sunday ahead before warm temps return Monday.
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