Thunder Bay three-day weather for August 26-28, 2026: Showers and northwest winds gusting to 40 km/h today, mainly cloudy Thursday

THUNDER BAY – WEATHER – Wednesday, August 26, 2026 – Thunder Bay starts Wednesday in misty, damp conditions, with scattered showers and strengthening northwest winds setting the weather story for the day. Conditions gradually improve Thursday before sunshine returns Friday.

On Western Lake Superior, mariners face scattered showers, fog early today and a risk of thunderstorms before conditions settle. Winds shift sharply from south to northwest, with waves rebuilding to around one metre this evening. Thursday remains breezy before light winds arrive Friday, potentially offering the best marine-weather window of the three-day period.

Today’s Weather Overview

Current Conditions

At 6:48 AM EDT, Thunder Bay Airport was reporting mist and 14.8°C.

Humidity was 100 percent, with the dew point also at 14.8°C. Barometric pressure was 100.7 kPa and falling, while winds were light from the southwest at 5 km/h.

Visibility was reduced to just 2 kilometres, so drivers should expect locally reduced visibility during the early morning commute.

Wednesday, August 26

Environment Canada’s forecast calls for cloudy skies with a 60 percent chance of showers.

Northwest winds develop this morning at 20 km/h with gusts to 40 km/h. The high reaches 23°C, with the humidex making it feel closer to 28.

The combination of high humidity, showers and gusty northwest winds will make Wednesday changeable. Outdoor activities remain possible, but a waterproof layer is worth carrying.

Wednesday Night

Tonight will be mainly cloudy with a 30 percent chance of showers during the evening.

Northwest winds continue at 20 km/h with gusts to 40 before becoming light later this evening.

The temperature falls to 12°C overnight.

Thursday, August 27 — Cooler and Mainly Cloudy

Thursday brings quieter weather to Thunder Bay.

Environment Canada is forecasting mainly cloudy skies, with northwest winds around 20 km/h shifting northeast at 20 km/h during the afternoon.

The high reaches 21°C, slightly below the seasonal normal daytime maximum of 22°C.

Thursday night clears and becomes considerably colder, with the temperature falling to just 7°C. That will make Friday morning feel distinctly autumn-like despite the calendar still showing August.

Friday, August 28 — Sunshine Returns

Friday currently offers the best weather in the three-day outlook.

Environment Canada is calling for sunny skies and a high of 22°C, putting the afternoon right around the seasonal normal.

Friday night remains clear, with an overnight low of 10°C.

For hiking, yard work, cycling, a trip to camp or other outdoor plans, Friday looks like the most favourable day of the forecast period.

Lake Superior West Marine Weather

Western Lake Superior — Wednesday

Environment Canada’s Western Lake Superior marine forecast, issued at 3:00 AM EDT Wednesday, calls for south winds at 15 knots early today.

Those winds diminish to variable 10 knots this morning, then swing around and increase to northwest 15 knots early this evening.

For comparison, 15 knots is approximately 28 km/h, while 10 knots is about 19 km/h.

Waves

Waves of 0.5 to 1 metre early today subside to 0.5 metre or less this morning.

As northwest winds strengthen, waves build again to around 1 metre early this evening.

This means the calmer open-lake window is expected during the middle portion of the day, although the weather itself remains unsettled.

Showers, Fog and Thunderstorm Risk

Scattered showers continue today and are forecast to end near midnight.

There is also a risk of thunderstorms on Western Lake Superior, while morning fog patches should dissipate near noon.

The thunderstorm risk is important for boaters because winds, visibility and wave conditions can change very quickly near a storm.

Environment Canada reported no marine watches or warnings in effect for Western Lake Superior with the 3:00 AM forecast.

Thursday Marine Forecast

Northwest winds near 15 knots continue through much of Thursday before diminishing to northwest 10 knots Thursday evening.

Scattered showers are possible Thursday afternoon.

Waves that build to around one metre Wednesday evening are forecast to subside to 0.5 metre or less Thursday evening.

Conditions should therefore gradually become more manageable later Thursday, particularly as winds and waves decrease.

Friday Marine Forecast

Friday currently looks considerably quieter on Western Lake Superior.

Environment Canada’s extended marine forecast calls for light winds Friday.

The current extended forecast does not provide a specific Friday wave height, so boaters should check the updated marine forecast before departure rather than assuming calm seas solely from the light-wind outlook.

If the forecast holds, Friday should offer the best combination of sunny weather in Thunder Bay and light winds on western Lake Superior during this three-day period.

Boating and Outdoor Outlook

Wednesday demands the most attention from mariners. Fog, scattered showers, a thunderstorm risk and a major wind-direction shift all factor into conditions on western Lake Superior.

The lighter variable winds expected for part of Wednesday morning may provide a temporary calmer period, but northwest winds strengthen again toward evening and waves rebuild to around one metre.

Thursday gradually improves, especially later in the day as waves subside.

Friday currently stands out as the best boating day, with light winds forecast on Lake Superior and sunny skies over Thunder Bay. Mariners should still check Environment Canada’s newest forecast and any warnings immediately before leaving shore.

Wardrobe Recommendations

Wednesday calls for layers and rain protection. A lightweight waterproof jacket will help with passing showers, while the northwest gusts will make a wind-resistant shell useful by afternoon.

Temperatures near 23°C should still feel comfortable in lighter clothing when showers are absent.

Thursday will be somewhat cooler, and the biggest wardrobe consideration comes Thursday night when temperatures fall to 7°C. A hoodie, fleece or light jacket will be useful for evening activities and early Friday travel.

Friday’s sunshine and 22°C high support lighter daytime clothing, but anyone heading onto Lake Superior should keep an extra wind-resistant layer aboard. Conditions over the lake can feel considerably cooler than inland temperatures.

Weather Trivia

Thunder Bay’s seasonal normal for August 26 is approximately a high of 22°C and a low of 9°C. Wednesday’s forecast high of 23°C is almost exactly seasonal, while Thursday night’s forecast low of 7°C will be a couple of degrees colder than normal.

Sunrise Wednesday is at 7:06 AM EDT, with sunset at 8:51 PM EDT. Thunder Bay now has less than 14 hours of daylight as the region moves toward September.

Lake Superior’s influence remains important at this time of year. Its enormous volume changes temperature far more slowly than the surrounding land, helping create sharp differences between conditions along exposed shorelines and locations farther inland.

Sources: Environment and Climate Change Canada Thunder Bay observations and public forecast issued 5:30 AM EDT Wednesday, August 26, 2026, and Western Lake Superior marine forecast issued 3:00 AM EDT Wednesday.

Overview

Thunder Bay three-day weather for August 26-28, 2026: Showers and northwest winds gusting to 40 km/h today, mainly cloudy Thursday and sunshine Friday. Western Lake Superior sees shifting winds, thunderstorms and one-metre waves before light winds Friday.