THUNDER BAY – WEATHER – Saturday, September 12, 2026 – Thunder Bay kicks off the weekend under mostly cloudy skies, with some rain possible and strong west winds picking up.
Saturday is expected to be the warmest day of the three-day forecast. Cooler temperatures will move in on Sunday, while the chance for rain lingers into Monday.
The weather looks promising for the Wake the Giant festival at Marina Park and other events like the Downtown Throwdown along Red River Road in the Waterfront District today. Be sure to check out The Good Harvest on Sunday along Red River Road between Court and St. Paul Street as well. There will also be vendors inside Goods & Co.
Saturday, September 12
The morning should see showers wrapping up, followed by mainly cloudy skies and a 40 percent chance of more rain later. There’s also a risk of thunderstorms early in the morning.
West winds will hit 30 km/h with gusts reaching up to 50 km/h. The high temperature for the day will be around 21°C, with a moderate UV index of 4.
Saturday night will remain mostly cloudy with a 30 percent chance of showers. Winds will calm down in the evening, and temperatures are expected to drop to about 7°C.
Sunday, September 13
Sunday’s forecast shows mostly cloudy skies and noticeably cooler weather, along with a 30 percent chance of morning showers.
West winds will again reach speeds of 30 km/h with gusts up to 50 km/h. Expect a high near 16°C, accompanied by a moderate UV index of 3.
The night sky should clear up on Sunday as temperatures fall to around 3°C. Gardeners in sheltered areas outside Thunder Bay should keep an eye on forecasts since temperatures might approach freezing levels.
Monday, September 14
On Monday, expect a mix of sun and clouds along with a 30 percent chance for showers.
The daytime high is expected to reach around 16°C. Monday night will likely become cloudy with a higher chance of showers at about 40 percent and lows near 12°C.
You might want to have an umbrella or rain jacket ready just in case, but it’s not looking like Monday will be completely rainy.
Three-Day Thunder Bay Outlook
Day Conditions High Low Saturday Mainly cloudy; 40% chance of showers; west wind gusting to 50 km/h 21°C 7°C Sunday Mainly cloudy; 30% chance of morning showers; west wind gusting to 50 km/h 16°C 3°C Monday Mix of sun and cloud; 30% chance of showers 16°C 12°C
Travel and Outdoor Planning
Please note that wind gusts reaching up to 50 km/h may impact taller vehicles and make biking trickier on Saturday and Sunday. Brief downpours could lower visibility and create slippery roads at times.
The forecast can change rapidly. Before heading out, make sure to check for any alerts or updates from Environment and Climate Change Canada along with current highway conditions through Ontario 511.
Summary: The weather from September 12-14 in Thunder Bay suggests windy conditions paired with potential rain on Saturday and Sunday, continuing into Monday as well.
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