THUNDER BAY – WEATHER – Thunder Bay is starting Sunday on a crisp, mainly sunny note, with calm winds and excellent visibility. The day will warm nicely, climbing from 6.1°C early this morning to a forecast high of 21°C, making for a bright late-spring day across the city.
Today’s Weather Overview
Current Conditions
At 8:00 AM EDT Sunday, May 31, 2026, conditions at Thunder Bay Airport were mainly sunny with a temperature of 6.1°C. The dew point was 3.0°C, with humidity at 81 percent, giving the morning a cool and slightly damp feel.
Winds are light from the southwest at 4 km/h, visibility is strong at 32 km, and the barometric pressure is 102.3 kPa and falling. Despite the cool start, the forecast calls for full sunshine today with a high of 21°C. The UV index is 8, or very high, so sun protection will be important for anyone spending time outdoors.
Tomorrow’s Forecast
Expected Conditions
Tonight: Skies will remain clear, with the temperature dropping to a low of 4°C. It will be a cool night, especially in low-lying areas and away from the city core.
Monday, June 1: Thunder Bay will see another sunny day, though slightly cooler than Sunday. Winds will be east at 20 km/h, becoming light early in the afternoon. The high will reach 18°C, with a UV index of 1, or low. Monday night will be clear with a low of 4°C.
Tuesday, June 2: Sunshine continues with a high of 22°C. Tuesday night will be clear with a low of 7°C.
Wednesday, June 3: A warmer and more unsettled pattern arrives. Expect a mix of sun and cloud with a 40 percent chance of showers and a high of 27°C. Wednesday night will bring cloudy periods with a 60 percent chance of showers and a low of 11°C.
Wardrobe Recommendations
A jacket or sweater is a good choice early this morning, with temperatures near 6°C. By afternoon, lighter spring clothing will be comfortable as the temperature rises to 21°C.
For outdoor plans, bring sunglasses, sunscreen, and a hat because of the very high UV index today. Monday morning will again be cool near 4°C, so early commuters and walkers should keep a warm layer handy.
Weather Trivia
Environment Canada lists Thunder Bay’s normal temperatures for this time of year at a maximum of 19°C and a minimum of 6°C. Today’s forecast high of 21°C is slightly above normal, while tonight’s low of 4°C is a little cooler than the seasonal average.
