September 8-10, 2026: Thunder Bay Forecast — Rain and Thunder Tuesday, Windy Wednesday, Sunny Thursday
THUNDER BAY – WEATHER – Tuesday, September 8, 2026 – Thunder Bay starts Tuesday wet and humid, with showers and a thunderstorm risk before stronger winds arrive later today and Wednesday.
It is actually not bad out this morning even with the rain. Don’t let a few sprinkles of rain make your day slow down.
The Thunder Bay forecast will see weather turn noticeably cooler and windier Wednesday, then conditions will improve sharply Thursday with sunshine and a high back into the low 20s.
Today’s Weather Overview
Current Conditions
At 6:00 a.m. EDT Tuesday, Thunder Bay Airport was reporting light rain and 17.3°C.
Humidity was 100 percent, barometric pressure was 101.7 kPa and falling, and winds were light from the north-northeast at 3 km/h. Visibility was 16 kilometres.
Tuesday, September 8
Showers continue through the morning before ending early this afternoon.
There is a risk of a thunderstorm this morning, with local rainfall amounts of 20 to 30 mm possible.
South winds increase to 20 km/h gusting to 40 km/h.
The high reaches 21°C, with a humidex of 28 and a moderate UV index of 3.
Tonight stays mainly cloudy with a 30 percent chance of showers and an evening thunderstorm risk.
West winds continue at 20 km/h gusting to 40 km/h, with a low of 14°C.
Wednesday, September 9
Wednesday will be the windiest day of the forecast.
Expect cloudy skies with a 40 percent chance of showers late in the morning and afternoon.
West winds increase from 20 km/h gusting to 40 to 40 km/h gusting to 60 km/h during the morning.
The high reaches 20°C.
Wednesday night turns much cooler, with cloudy periods, a 40 percent shower chance and a low of just 7°C.
Thursday, September 10
Thursday brings the clear improvement.
Environment Canada is forecasting sunny skies and a high of 21°C.
Thursday night brings cloudy periods and a low near 10°C.
Three-Day Weather Trend
Tuesday: Wet and humid, with showers, possible thunder and 20 to 30 mm of rain. High 21°C.
Wednesday: Cooler and much windier, with west gusts reaching 60 km/h and scattered showers. High 20°C.
Thursday: Sunny and calmer. High 21°C.
Travel and Outdoor Outlook
Tuesday morning is the poorest period for outdoor plans because of rain and the thunderstorm risk.
Wednesday may be drier at times, but strong west winds could make conditions uncomfortable for cycling, exposed walking routes and high-profile vehicles.
Thursday is the best outdoor day of the three.
Drivers should be prepared for reduced visibility during heavier Tuesday showers and should use extra caution Wednesday where strong crosswinds affect exposed sections of Highways 11/17, 61, 102 and 130.
Wardrobe Recommendations
Tuesday calls for a waterproof jacket and footwear.
Wednesday will feel cooler than the thermometer suggests because of strong winds, so a wind-resistant jacket or light fleece will be useful.
Thursday is a more comfortable late-summer day, although the morning will feel cool after Wednesday night’s 7°C low.
Weather Trivia
Thunder Bay’s normal early-September high is about 19°C, with a normal low near 6°C.
That means daytime temperatures remain close to or slightly above seasonal values through Thursday, while Wednesday night comes very close to the normal overnight low.
Source: Environment and Climate Change Canada Thunder Bay forecast issued at 5:30 a.m. EDT Tuesday, September 8, 2026.
Summary
Thunder Bay weather for September 8-10, 2026: Showers, thunderstorms and 20-30 mm of rain Tuesday give way to west winds gusting to 60 km/h Wednesday before sunshine returns Thursday.
