THUNDER BAY – WEATHER DESK – Tuesday, September 29, 2026 – Thunder Bay will see a changeable three-day stretch, beginning with showers and a risk of a thunderstorm today. Wednesday will be warm for late September, with a Humidex near 27, before cooler air arrives Thursday.
At 6:00 a.m. Tuesday, Thunder Bay Airport reported mostly cloudy skies, 14 C, an east-northeast wind at 7 km/h, 89% humidity and visibility of 24 kilometres.
Weather Alerts
No Environment and Climate Change Canada warning, watch or advisory was displayed for Thunder Bay during the morning check. Alerts can change quickly, so residents should review the official ECCC alert page before travel or outdoor work.
Tuesday, September 29: Showers and Thunderstorm Risk
Expect cloudy skies with a 40% chance of showers this morning and early this afternoon. A few showers will begin again this afternoon, with a risk of a thunderstorm. The wind will become south at 20 km/h near noon. The high will be 19 C.
Showers should end this evening, but cloudy skies and a 60% chance of showers or drizzle will continue. There is a risk of a thunderstorm early this evening. Fog patches may develop after midnight. The low will be 12 C.
Wednesday, September 30: Warm with Morning Drizzle
Wednesday will be mainly cloudy, with a 40% chance of drizzle in the morning and early afternoon. Skies should clear late in the afternoon. Fog patches are expected to dissipate during the morning.
The wind will become south at 20 km/h in the afternoon. The high will reach 22 C, with a Humidex near 27. Wednesday night will be cloudy with a low of 10 C.
Thursday, October 1: Cooler with Some Sunshine
Thursday will bring a mix of sun and cloud. The high will be 16 C. Cloudy periods are expected overnight, with a low near 3 C.
Thunder Bay Forecast at a Glance
| Date | Conditions | High | Night |
|---|---|---|---|
| Tuesday, Sept. 29 | Cloudy; 40% chance of showers; afternoon thunderstorm risk; south wind 20 km/h | 19 C | Showers or drizzle; low 12 C |
| Wednesday, Sept. 30 | Mainly cloudy; 40% chance of morning drizzle; clearing late; south wind 20 km/h; Humidex 27 | 22 C | Cloudy; low 10 C |
| Thursday, Oct. 1 | Mix of sun and cloud | 16 C | Cloudy periods; low 3 C |
Travel and Outdoor Advice
Wet pavement, drizzle and fog may reduce visibility and traction, especially this evening and overnight. Drivers should slow down, use low-beam headlights and leave extra following distance.
Thunderstorms may bring brief heavy rain and sudden wind changes. Outdoor workers should secure lightweight materials and pause exposed work if thunder is heard. Boaters on Thunder Bay, Lake Superior and nearby inland lakes should check the latest marine forecast, wear a flotation device and move to shelter when storms approach.
Sources Checked
- Environment and Climate Change Canada Thunder Bay forecast and airport observation, forecast issued at 5:30 a.m. EDT Tuesday, September 29, 2026.
- Environment and Climate Change Canada active alerts, checked Tuesday morning.
