Weather and Calm Western Lake Superior Conditions
THUNDER BAY – WEATHER – Thursday, September 3, 2026 – Thunder Bay is heading into a generally quiet three-day stretch, with a mix of sun and cloud today, more cloud Friday, and another mild day Saturday.
Temperatures remain above seasonal normals through the period, with highs of 24°C today, 22°C Friday and 24°C Saturday. Western Lake Superior is also looking unusually calm for early September, with light winds today, only a modest east to northeast flow tonight and Friday, and waves remaining 0.5 metres or less.
Today’s Weather Overview
Current Conditions
At 6:00 AM EDT, Thunder Bay Airport was reporting 9.9°C.
Humidity was 100 percent, with the dew point also at 9.9°C. Barometric pressure was 101.5 kPa, and winds were from the west-southwest at 7 km/h.
Thursday, September 3
Thunder Bay will see a mix of sun and cloud today.
The high reaches 24°C, with a humidex of 29. The UV index is 6, or high.
Tonight brings a few clouds followed by increasing cloudiness overnight, with a low of 12°C.
Friday, September 4
Friday turns cloudy, but remains mild.
The high reaches 22°C, with a humidex of 27 and a moderate UV index of 4.
Friday night remains cloudy with a low of 13°C.
Saturday, September 5
Saturday remains cloudy, but temperatures climb back to 24°C.
Saturday night stays cloudy with a low of 14°C.
Lake Superior West Marine Forecast
Thursday Marine Conditions
Environment Canada’s Western Lake Superior marine forecast calls for light winds today.
Winds become east 10 knots overnight, then back to northeast 10 knots Friday evening.
For reference, 10 knots is approximately 19 km/h.
Waves
Waves are forecast to remain 0.5 metres or less today, tonight and Friday.
That makes for relatively favourable boating conditions, particularly compared with the stronger winds and larger waves seen earlier in the week.
Marine Warnings
Environment Canada reported no watches or warnings in effect for Western Lake Superior with the 3:00 AM marine forecast.
Friday Marine Outlook
Friday remains quiet on the lake.
East winds around 10 knots gradually back to northeast 10 knots Friday evening, with waves continuing at 0.5 metres or less.
That should keep open-water conditions manageable for most recreational craft, although nearshore conditions can still vary with shoreline exposure.
Saturday Marine Outlook
Environment Canada’s extended forecast calls for light winds Saturday on Western Lake Superior.
Sunday also currently carries light winds, while southeast winds may increase to 15 knots later Monday.
Saturday therefore looks like another favourable day for boating if the forecast holds.
Boating Outlook
Thursday through Saturday provides one of the quieter marine stretches in the immediate forecast.
Thursday: Light winds and waves at or below 0.5 metres.
Friday: East to northeast winds near 10 knots, with waves still 0.5 metres or less.
Saturday: Light winds expected.
Mariners should still check the latest Environment Canada marine forecast before departure, especially if travelling beyond sheltered areas of Thunder Bay Harbour.
Wardrobe Recommendations
Thursday will feel pleasantly warm in the afternoon, so lighter clothing should be comfortable once temperatures rise.
A light jacket or hoodie will still be useful early this morning and again after sunset.
Friday’s added cloud may make 22°C feel slightly cooler, while Saturday returns to a milder 24°C.
Anyone heading onto Lake Superior should carry a wind-resistant layer, even with light winds, as open-water conditions can feel cooler than inland temperatures.
Weather Trivia
Thunder Bay’s normal high for early September is around 20°C, with a normal low near 7°C.
That means Thursday and Saturday’s forecast highs of 24°C are about four degrees above normal, while even Friday’s 22°C remains slightly warmer than seasonal.
Sources: Environment and Climate Change Canada Thunder Bay forecast issued 5:30 AM EDT Thursday, September 3, 2026, and Western Lake Superior marine forecast issued 3:00 AM EDT Thursday.
