A warm Friday brings a high of 28°C, humidex 31, very high UV, and thunderstorm risk before a sunny, cooler weekend
Thunder Bay – Weather – Thunder Bay is starting Friday on a cool, mainly sunny note, but the weather story changes quickly through the day. A warm afternoon is ahead, with temperatures climbing toward 28°C, a humidex near 31, and a risk of thunderstorms later today before a cooler, sunny weekend settles in.
The temperatures are finally hitting a point where plants in the garden can safely be planted, without serious damage from overnight frost – no money back guarantee but the forecast is promising.
Today’s Weather Overview
Current Conditions
At 7:00 AM EDT Friday, May 29, 2026, conditions at Thunder Bay Airport were mainly sunny with a temperature of 7.2°C. The air is cool and damp early this morning, with the humidity at 90 percent and a dew point of 5.7°C.
Winds are light from the west-southwest at 6 km/h, visibility is excellent at 32 km, and the barometric pressure is 101.8 kPa and falling. That falling pressure fits with the changing pattern expected this afternoon, when sunshine gives way to more cloud and a chance of showers.
Today will become much warmer. The forecast calls for sunny skies this morning and early this afternoon, followed by a mix of sun and cloud with a 40 percent chance of showers this afternoon. There is also a risk of a thunderstorm. The high will reach 28°C, with a humidex of 31 and a UV index of 8, or very high.
Tomorrow’s Forecast
Expected Conditions
Tonight: Partly cloudy skies are expected with a 40 percent chance of showers early this evening and a continued risk of a thunderstorm. Winds will become east at 20 km/h before morning, and the overnight low will fall to 6°C.
Saturday, May 30: The weekend begins with a noticeable cooldown. Saturday will be sunny, with a high of 17°C and a UV index of 8, or very high. Saturday night will be clear, with a low of 8°C.
Sunday, May 31: Sunday looks like the best outdoor day of the weekend, with sunny skies and a high of 22°C. Sunday night will remain clear, with a low near 9°C.
Monday, June 1: Sunshine continues with a high of 19°C. Monday night will be clear with a low of 8°C.
Tuesday, June 2: Another sunny day is expected, with a high of 23°C. The overnight low will be 9°C.
Wednesday, June 3: Sunny skies continue, with a high near 22°C and a nighttime low of 10°C.
Thursday, June 4: A mix of sun and cloud is forecast, with a warmer high of 25°C.
Wardrobe Recommendations
Start the day with a light jacket or hoodie, especially for the morning commute, as temperatures are near 7°C early in the day. By afternoon, short sleeves will be comfortable as the temperature rises to 28°C, but sunscreen, sunglasses, and a hat are smart choices because of the very high UV index.
For Friday afternoon and early evening, keep a light rain jacket or umbrella nearby due to the shower and thunderstorm risk. Saturday will feel cooler, with a high of only 17°C, so a sweater or spring jacket will be useful, especially near Lake Superior. Sunday looks ideal for lighter spring clothing, with a pleasant high of 22°C, though evenings will still be cool.
Weather Trivia
Thunder Bay often sees sharp temperature swings in late May because Lake Superior remains cold while inland areas warm quickly under spring sunshine. A wind shift off the lake can cool conditions dramatically, even after a warm day.
Summary:
Thunder Bay weather for May 29, 2026: A warm Friday brings a high of 28°C, humidex 31, very high UV, and thunderstorm risk before a sunny, cooler weekend with highs of 17°C Saturday and 22°C Sunday.
