September 9-11, 2026: Thunder Bay Forecast — Windy Wednesday, Sunny Thursday, Showers Return Friday
THUNDER BAY – WEATHER – Wednesday, September 9, 2026 – Thunder Bay is in for a windy Wednesday before conditions improve significantly Thursday. Friday turns warmer, but another chance of showers develops.
On Western Lake Superior, strong west-to-northwest winds and waves near 2 metres make Wednesday the roughest boating day of the three. Winds ease Thursday before turning southerly and strengthening again Friday.
Today’s Weather Overview
Current Conditions
At 7:00 a.m. EDT Wednesday, Thunder Bay Airport was reporting mainly clear skies and 14.2°C.
Humidity was 83 percent, barometric pressure was 100.7 kPa and falling, southwest winds were light at 5 km/h, and visibility was an excellent 32 kilometres.
Wednesday, September 9
Cloud increases today with a 30 percent chance of showers late this morning and this afternoon.
West winds strengthen from 20 km/h gusting to 40 to 40 km/h gusting to 60 km/h this morning.
The high reaches 21°C, with a moderate UV index of 4.
Tonight becomes partly cloudy. West winds near 30 km/h ease late this evening, with a low of 8°C.
Thursday, September 10
Thursday provides the best weather of the three-day forecast.
Expect sunshine through the morning, becoming a mix of sun and cloud during the afternoon.
The high reaches 22°C.
Thursday night will be clear with a low of 11°C.
Friday, September 11
Friday remains warm but becomes less settled.
Expect a mix of sun and cloud with a 40 percent chance of showers and a high of 23°C.
Friday night turns cloudy with a 60 percent chance of showers and a mild low of 14°C.
Western Lake Superior Marine Conditions
Wednesday — Strong Winds and Rougher Water
The latest Environment Canada Western Lake Superior marine bulletin available carries a Strong Wind Warning.
West winds are forecast around 25 knots, or approximately 46 km/h, before turning northwest at 25 knots this evening.
Waves build to around 2 metres, with scattered showers possible later Wednesday.
For smaller recreational boats, Wednesday is the least favourable day of this forecast. Strong winds and two-metre waves can make exposed sections of Western Lake Superior challenging.
Thursday — Gradual Improvement
Northwest winds near 25 knots early Thursday diminish to 15 knots, or about 28 km/h, during the morning.
Winds then back to southwest at around 15 knots late in the day.
Conditions should improve as the strongest northwest winds ease, but boaters should check the latest wave forecast before leaving harbour.
Friday — Southerly Winds Strengthen
Friday begins with south winds near 15 knots, increasing to 20 knots, or roughly 37 km/h, late in the day.
That strengthening southerly flow could once again produce choppier conditions on exposed water by Friday afternoon and evening.
Boating Outlook
Wednesday is the roughest marine day, with strong west-to-northwest winds and waves around two metres.
Thursday offers the best marine window as winds ease, while Friday becomes breezier again later in the day.
Because marine forecasts can change quickly, boaters should check the latest Environment Canada Western Lake Superior forecast and warning status immediately before departure.
Travel and Outdoor Outlook
Strong west winds Wednesday may make cycling, walking in exposed areas and driving high-profile vehicles more difficult.
Thursday is the strongest outdoor day, with sunshine, lighter winds and a high of 22°C.
Friday remains warm enough for outdoor plans, but keep rain gear nearby as the shower risk increases.
Wardrobe Recommendations
Wednesday calls for a wind-resistant jacket, especially during the morning and afternoon.
Thursday will be comfortable in lighter clothing during the day, although the morning starts cool.
Friday is warmer, but a light waterproof layer will be useful with showers possible.
For anyone heading onto Lake Superior, wear a windproof and waterproof outer layer and dress for conditions cooler than those experienced inland.
Weather Trivia
Thunder Bay’s normal high for September 9 is about 18°C, with a normal low near 6°C.
All three forecast daytime highs — 21°C Wednesday, 22°C Thursday and 23°C Friday — are above normal for this point in September.
Sources: Environment and Climate Change Canada Thunder Bay forecast issued 5:30 a.m. EDT Wednesday, September 9, 2026, and Western Lake Superior marine forecast information available Wednesday morning.
Summary
Thunder Bay weather for September 9-11, 2026: West winds gust to 60 km/h Wednesday before sunny weather Thursday and warmer, showery conditions Friday. Western Lake Superior sees strong winds and waves near two metres Wednesday.
