Mostly Mild in the Bay – Spring Takes the Slow and Steady Route
THUNDER BAY – WEATHER REPORT – May 23, 2025 – If you like your spring weather on the laid-back side, Thunder Bay is serving up your ideal weekend. While it’s a bit shy on sunshine this Friday, a calm and comfortable forecast stretches into Sunday, with moderate highs, light winds, and a reminder that northern Ontario’s frost-free guarantee doesn’t quite kick in until June.
At Thunder Bay Airport, the current temperature is 6.1°C, paired with mostly cloudy skies and excellent visibility at 32 km. The dew point is 2.5°C, and humidity sits at 78%, keeping things cool and crisp. A north-northwest breeze at 9 km/h stirs the air gently, and the barometric pressure is 102.1 kPa and rising, indicating improving conditions as the weekend unfolds.
Your Weekend Forecast – Cloudy Charms and Frosty Hints
Today:
Expect mainly cloudy skies, with occasional bright spots breaking through. Winds from the north at 20 km/h will ease later this morning. The high reaches a respectable 15°C, and the UV index is 5, so keep the sunscreen handy if the sun makes a surprise appearance.
Tonight:
Partly cloudy conditions settle in, and temperatures dip to a chilly 3°C. There’s a risk of frost, especially in low-lying areas, so green thumbs, cover up your garden starts or bring the potted plants inside.
Saturday, May 24:
The day starts with a mix of sun and cloud, bringing another mild high of 15°C. The UV index ticks up to 6, so it’s a good day for an afternoon hike or patio coffee—just don’t forget your SPF.
Saturday Night:
Cloudy periods linger through the evening, and once again, temperatures drop to 3°C. It’s a night to layer up or cozy up indoors.
Sunday, May 25:
Spring gives us one more peaceful offering with another mix of sun and cloud and a high of 16°C. Light winds and dry conditions make it a fine day for any outdoor plans—just be ready with a sweater when the sun ducks behind a cloud.
Sunday Night:
Clear skies return to wrap up the weekend with a low of 4°C, slightly warmer than the previous nights but still brisk.
What to Wear – Dress Like It’s Still Thinking About Winter
This weekend calls for strategic layering. Mornings and evenings remain nippy, so jackets and cozy hoodies are essentials. Midday warmth allows for lighter wear—think long sleeves or a fleece you can tie around your waist when the sun makes an appearance. If you’re out late, a toque might not be out of place.
Historical Highs and Lows – Thunder Bay’s Springtime Spectrum
Looking back, Thunder Bay once basked in a sweltering 30.8°C on this day in 1980—unthinkable given today’s modest forecast. On the flip side, a frosty -3.4°C was recorded in 1963. This year’s numbers fall comfortably in the middle, proving that spring in the Bay is a gentle, if indecisive, creature.
Weather Trivia – The Big Lake Effect
Here’s a Thunder Bay fun fact: Lake Superior acts like a natural air conditioner. Its icy waters keep spring temperatures cooler and delay the arrival of true warmth. But come July? The same lake works magic to cool heatwaves. For now, though, it’s doing what it does best—reminding us that layers are always a good idea.
