Foggy start gives way to sunshine and a late-September warm-up before cooler, unsettled weather rolls in this weekend

Thunder Bay begins this Thursday morning under a blanket of dense fog and 100% humidity, but don’t let that fool you—sunshine and warmth are on the way. A late-September temperature boost today will make it feel more like summer than fall, with humidex values pushing near 29°C. However, cooler air and the risk of showers return by Friday night and Saturday.

Today’s Weather Overview

Current Conditions

As of 7:32 AM EDT at Thunder Bay Airport, the city is enveloped in fog with visibility down to 0.6 km. The temperature and dew point are both 8.4°C, indicating 100% humidity—prime conditions for low-lying morning fog.

Winds are light from the west-northwest at 7 km/h, and barometric pressure sits at 101.4 kPa and falling, signaling an approaching shift in weather by the weekend.

Forecast for Thursday:

• Fog patches dissipating by mid-to-late morning.

• A mix of sun and cloud for the rest of the day.

• Winds becoming west at 20 km/h later this morning.

• High of 24°C, with a humidex of 29°C—very warm for this time of year.

• UV index: 5 (moderate) — sunscreen still advised if you’re out midday.

Tonight:

• Clearing this evening as skies open up.

• Winds become light after sunset.

• Low: +5°C — a crisp and cool fall night.

Weekend Weather Outlook

Friday, September 26:

• Sunny skies return during the day.

• High of 18°C — cooler than Thursday but still pleasant.

• UV index: 5 (moderate).

• Night: Cloudy periods with a 40% chance of showers late in the evening.
  Low: 8°C.

Saturday, September 27:

• A mix of sun and cloud, with a 60% chance of showers, especially in the morning and early afternoon.

• High of 22°C — a brief warm-up again.

• Night: Skies clear out.
  Low: +5°C.

Sunday, September 28:

• Sunny and beautiful, with a high of 23°C.

• Night: Clear skies continue.
  Low: 6°C.

Wardrobe Recommendations

It’s a week of weather contrasts, so dress smart with layers:

• Today (Thursday):

  • Start with a warm layer for the foggy morning.

  • Shed layers by afternoon—short sleeves or light long sleeves will be ideal with the humidex near 29°C.

• Friday:

  • Cooler daytime temperatures mean long sleeves or a light jacket will be more comfortable.

  • Have rain gear handy for the evening.

• Saturday:

  • A light raincoat or water-resistant layer will be helpful if showers develop.

  • By Sunday, you’ll be back in sunglasses and fall-friendly lighter layers.

Weather Trivia

Did you know?
Thunder Bay often experiences temperature spikes in the final week of September, known as a “false summer” or “Indian summer.” These occur when warm air masses move in from the Prairies and the U.S. Midwest. Today’s humidex of 29°C is well above average for this time of year—normal highs are closer to 15°C. This may be one of the warmest late-September days of the year!

Enjoy today’s warm spell while it lasts—and stay prepared for changing conditions by the weekend. Stay connected with the NetNewsLedger Weather Desk for continued updates.