Dense fog blankets the region early today—clearing to sunshine later, with a mixed pattern ahead.

Thunder Bay – WEATHER – A Fog Advisory is in effect for Thunder Bay this morning, as thick fog drastically reduces visibility to near zero in many areas. Drivers and early commuters should exercise extreme caution. Fortunately, the fog is expected to lift later this morning, revealing another mild and sunny day. A changeable pattern continues into the weekend with showers possible Friday before another warm-up Saturday.

Today’s Weather Overview

Current Conditions

As of 5:00 AM EDT from Thunder Bay Airport, the city is shrouded in dense fog, with visibility reduced to just 0.4 km. The temperature is 10.1°C, with a dew point also at 10.1°C, giving us 100% humidity—perfect conditions for persistent fog formation.

Winds are light from the northwest at 8 km/h, and pressure is steady at 102.0 kPa and rising, suggesting improving conditions later today.

A Fog Advisory issued by Environment Canada remains in effect:

Visibility may be significantly and suddenly reduced to near zero.
Travel is expected to be hazardous in some areas due to shifting fog patches.
If driving, slow down, use low beams, and be alert for sudden changes in visibility.

As the sun rises, clearing is expected late this morning, with a high of 20°C by the afternoon. The UV index will reach 6, or high, so sun protection will be needed later in the day despite this foggy start.

Tonight, skies will remain mostly clear with a few clouds, and fog patches may redevelop overnight. Expect an overnight low of 10°C.

Extended Forecast

Expected Conditions

• Thursday, September 11:
  Sunny skies throughout the day, with a slightly cooler but still pleasant high of 19°C.
  Night: Cloudy periods move in during the evening, with an overnight low of 9°C.

• Friday, September 12:
  Skies turn cloudy with a 30% chance of showers, especially in the afternoon. The high will be 18°C.
  Night: Cloudy conditions continue, with a milder low of 13°C.

• Saturday, September 13:
  The skies clear out again, bringing a warmer high of 23°C—a late-summer feel returns!
  Night: A few cloudy periods, with a low around 10°C.

Wardrobe Recommendations

With fog in the morning and sun later in the day, layering is your best strategy:

• This Morning: Wear a light jacket or hoodie, especially in areas affected by fog. Reflective gear is helpful if walking or biking in low visibility.

• Afternoons (Wednesday–Saturday): Temperatures will range between 18–23°C, so long sleeves or light layersare ideal. Sunglasses and sunscreen are a must on Thursday and Saturday.

• Evenings: Nights will stay around 9–13°C. A sweater or light coat will keep you comfortable, especially if fog redevelops.

Weather Trivia

Did you know?
Thunder Bay often experiences radiation fog in the fall—especially during calm, clear nights like we saw Tuesday. This type of fog forms when ground heat radiates into the night sky, cooling the surface enough to condense moisture. With Lake Superior nearby, fog can persist well into mid-morning, as seen today.

In fact, September is one of the foggiest months of the year for the city—so this morning’s conditions are quite typical!