Frosty Start to a Sunny Day in Thunder Bay

THUNDER BAY – WEATHER – Thunder Bay woke up to a chilly reminder that spring isn’t always warm and fuzzy. As of 6:00 AM EDT, temperatures were sitting at a brisk 1.9°C with nearly saturated air at 98% humidity. The winds are calm out of the west at 6 km/h, and the barometric pressure is on the rise at 101.2 kPa, signalling stable conditions for the day ahead. If you stepped outside and thought it felt more like early April—you weren’t wrong!

From Shivers to Sunshine – A Classic Northern Ontario Day

Today’s forecast is simple and spectacular: clear, sunny skies with a high of 20°C. Winds will shift to the northeast at 20 km/h, becoming light this afternoon. With a UV index of 8 (very high), sunscreen is your best friend—even if the morning frost made it feel like jacket weather.

Tonight at Port Arthur Stadium the callout is for fans to help cheer the Thunder Bay Border Cats onto victory lane after a hard Friday night lost. First pitch is at 6:35!

Tonight will stay clear and calm, with an overnight low of 5°C—another crisp evening perfect for stargazing or sleeping with the windows open (just maybe keep an extra blanket nearby).

On Sunday, a few morning clouds will give way to sunshine, though local wildfire smoke may drift into the area during the afternoon. The high remains pleasant at 20°C, and the UV index will again be high at 8.

Monday continues the stretch of beautiful weather with sunny skies and a high of 21°C, though clouds and a 30% chance of showers return Monday night.

Wardrobe Wisdom: Layers to the Rescue

Mornings like today are made for light gloves and a toque, even if you’ll be down to short sleeves by mid-afternoon. Dress in layers—Northern Ontario style—and don’t forget sunglasses and sunscreen for the midday hours.

Thunder Bay Weather Trivia

Did you know? The coldest May 31st in Thunder Bay history dropped to -2.2°C, so today’s frosty 1.9°C isn’t out of the ordinary. With its location on Lake Superior’s northwestern shore, Thunder Bay often sees extreme spring temperature swings, thanks to lake breezes and inland air mass collisions. One moment you’re scraping your windshield, and by lunch, you’re hunting for ice cream.

Looking Ahead

With consistent sunshine and no major systems on the horizon until early next week, it’s a perfect weekend to get outside—though if wildfire smoke does roll in Sunday, be cautious if you have respiratory concerns.