THUNDER BAY — WEATHER — Saturday, September 12, 2026 — Thunder Bay begins the weekend under mainly cloudy skies, with showers possible and gusty west winds developing.
Saturday will be the warmest day of the three-day forecast. Cooler air arrives Sunday, while the chance of showers continues into Monday.
The weather is looking good for the Wake the Giant festival at Marina Park as well as other events including the Downtown Throwdown along Red River Road in the Waterfront District today. On Sunday make plans to attend The Good Harvest as well along Red River Road between Court and St. Paul Street. There will also be venders inside Goods & Co.
Saturday, September 12
Showers will end during the morning, followed by mainly cloudy skies and a 40 per cent chance of additional showers. There is a risk of a thunderstorm early in the morning.
West winds will reach 30 km/h with gusts to 50 km/h. The daytime high will be 21°C, with a moderate UV index of 4.
Saturday night will remain mainly cloudy with a 30 per cent chance of showers. The wind will ease during the evening, and the temperature will fall to 7°C.
Sunday, September 13
Sunday will be mainly cloudy and noticeably cooler, with a 30 per cent chance of showers during the morning.
West winds will again reach 30 km/h with gusts to 50 km/h. The high will be near 16°C, with a moderate UV index of 3.
Skies will clear Sunday night and the temperature will fall to about 3°C. Gardeners in sheltered and rural areas around Thunder Bay should monitor the latest forecast in case temperatures approach the frost point.
Monday, September 14
Monday will bring a mix of sun and cloud with a 30 per cent chance of showers.
The daytime high will reach about 16°C. Monday night will turn cloudy with a 40 per cent chance of showers and a low near 12°C.
Keep an umbrella or rain jacket handy, but Monday is not expected to be a washout.
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
Wind gusts of up to 50 km/h may affect high-profile vehicles and make cycling more difficult on Saturday and Sunday. Brief showers could reduce visibility and make roads slippery at times.
Forecasts can change. Before travelling, check the latest alerts and forecast from Environment and Climate Change Canada and current highway conditions through Ontario 511.
Summary: Thunder Bay’s September 12–14 forecast calls for gusty winds and possible showers Saturday and Sunday, with a continued shower chance Monday.
