Thunder Bay Weather Forecast – Cool Winds Today, Clear Skies Just Around the Corner
A Breezy and Brisk Start with Clouds Creeping In
Thunder Bay, ON – Thursday, May 22, 2025: After yesterday’s sunshine, Thunder Bay is taking a brief pause to flirt with more cloud cover and cooler air. As of 6:00 AM, it’s 4.6°C at Thunder Bay Airport under mostly cloudy skies. With humidity at 82% and a dew point of 1.8°C, the morning feels damp and a little raw. Winds are light for now — from the west-northwest at 4 km/h — but don’t get too comfortable. The barometric pressure is 101.9 kPa and falling, which means change is on the way.
As the morning moves along, expect skies to turn fully cloudy, and winds will strengthen, shifting to the north at 20 km/h with gusts up to 40 km/h. That breeze will bite, especially if you’re out along the lakeshore. Temperatures will peak at 15°C this afternoon, but with the cloud cover and wind, it may not feel quite that warm. The UV index is a moderate 4, so a touch of sun protection isn’t a bad idea if you’re outdoors during any breaks in the cloud.
Cloudy and Cold Tonight with Frost a Possibility
Tonight, the clouds persist under overcast skies, and winds from the north will continue to gust at 20 km/h to 40 km/h. The temperature drops to +3°C, and with those clear pockets and cooler air, there’s a risk of frost, especially in low-lying rural areas. Gardeners may want to throw a blanket over their tender greens — just to be safe.
Friday’s Chill Lingers Before Weekend Warm-Up
Friday continues the cloudy theme, with north winds at 20 km/h, easing late in the morning. The high will reach 12°C, keeping things on the cooler side, and the UV index remains moderate at 4. By Friday night, skies will finally clear out, and we’ll dip again to a low of +3°C — another frosty risk in spots, though calmer winds may ease the chill.
The Weekend Forecast: Sunshine and Seasonal Relief
Saturday delivers the payoff we’ve been waiting for — sunny skies and a high of 19°C. It’s finally the kind of spring weather that justifies dragging your lawn furniture out of the garage. Saturday night remains clear with a low of +3°C.
Sunday follows suit with sunny skies and a slightly cooler high of 17°C, but it will still feel great compared to the gray skies of midweek. Another clear night and another low of +3°C wrap up what looks to be a beautiful spring weekend in Thunder Bay.
What to Wear?
Today is a layered-clothing kind of day: start with a wind-resistant jacket for the chilly gusts, and something warm underneath for the cool morning air. Keep that umbrella packed away — it won’t be needed — but gloves might still come in handy if you’re out early. And if you’re gardening, be ready to cover those frost-sensitive plants tonight.
Historic Temperatures for May 22
On this day, Thunder Bay has felt the full range of spring moods — the record high is a toasty 29.8°C, while the record low dipped to -4.0°C. Today’s 15°C high lands us somewhere comfortably in the middle, if a little on the cloudy side.
Thunder Bay Weather Trivia
Did you know Thunder Bay’s position near Lake Superior gives it one of the most variable spring climates in Canada? On some days, you can experience all four seasons — often before lunch. That lake-cooled air keeps things brisk this time of year, but it also delivers some of the clearest skies once high pressure settles in. Like this weekend!
