Thunder Bay weekend weather for August 22-23, 2026: Saturday brings sun, northwest winds gusting to 40 km/h and a 30% chance of late showers before a sunny 22°C Sunday.
Thunder Bay – WEATHER DESK – Thunder Bay is heading toward a generally favourable late-summer weekend, although Saturday will come with a few weather complications. Sunshine Saturday morning gives way to more cloud, gusty northwest winds and a 30 percent chance of late-afternoon showers. Sunday is easily the better outdoor day, with sunshine and a comfortable high near 22°C.
People heading to camp, spending time along the Lake Superior shoreline or planning boating and fishing trips should pay particular attention to Saturday’s northwest wind, which is forecast to gust to 40 km/h. By Sunday, conditions become quieter and brighter.
Today’s Weather Overview
Current Conditions — Friday Morning
At 6:00 AM EDT Friday, Thunder Bay Airport was reporting cloudy skies and 14.2°C.
Humidity was very high at 99 percent, with a dew point of 14.1°C. Barometric pressure stood at 101.3 kPa and falling, while north winds were light at 4 km/h. Visibility was 24 kilometres.
Friday itself will remain mainly cloudy as morning fog patches dissipate. The temperature reaches about 20°C, with a humidex of 26 and a high UV index of 6.
Friday night introduces some instability ahead of the weekend. Thunder Bay will be partly cloudy with a 40 percent chance of showers this evening and after midnight, along with a risk of a thunderstorm. The overnight low will be 12°C.
Weekend Forecast
Saturday, August 22 — Sun, Wind and a Late Shower Chance
Saturday begins on a promising note with sunny skies early in the morning. A mix of sun and cloud develops as the day progresses, with a 30 percent chance of showers late in the afternoon.
The bigger factor for outdoor plans will be the wind. Northwest winds increase to 20 km/h with gusts reaching 40 km/h during the morning.
Saturday’s high reaches 23°C, with a humidex of 25. The UV index will be 6, or high.
That makes the morning and early afternoon the better portion of Saturday for yard work, hiking, outdoor events or a trip to camp. The late-afternoon shower probability does not mean everyone will see rain, but keeping a rain jacket handy is sensible.
For boaters, anglers and paddlers, the northwest gusts deserve more attention than the modest shower probability. Conditions on exposed portions of Lake Superior and larger inland lakes can be considerably rougher than conditions near shore.
Saturday Night
Cloudy periods continue Saturday night with about a 30 percent chance of showers.
Temperatures drop sharply to around 8°C, bringing a distinctly cool late-summer night.
Campers and anyone staying outdoors into the evening should be prepared for the quick temperature drop once the sun goes down.
Sunday, August 23 — The Weekend Winner
Sunday currently offers the best weather of the weekend.
Environment Canada is forecasting sunny skies and a high of 22°C. There is no precipitation mentioned in the current Sunday daytime forecast.
For walking, cycling, hiking, golf, gardening, a trip to Marina Park or other outdoor plans, Sunday should provide an excellent combination of sunshine and comfortable temperatures.
Sunday night remains clear, with the temperature dropping to 9°C.
The cool overnight temperature is worth remembering for anyone camping outside the city or planning an early Monday start.
Looking Ahead to Monday
The pleasant weather carries into the beginning of the work week.
Monday, August 24 is forecast to be sunny with a high near 23°C. Clouds increase Monday night with a 30 percent chance of showers.
By Tuesday, a more unsettled pattern returns with a 40 percent chance of showers.
Wardrobe Recommendations
Saturday calls for flexible layers. A T-shirt or other light summer clothing should be comfortable during the afternoon high near 23°C, but a light windbreaker will be useful with northwest gusts reaching 40 km/h.
Keep a light rain jacket handy Saturday afternoon in case one of the scattered showers develops over the city. With the UV index reaching the high category, sunscreen, sunglasses and a hat remain worthwhile even with periods of cloud.
Saturday evening will cool rapidly. A hoodie, fleece or light jacket will be useful as temperatures head toward 8°C.
Sunday is straightforward summer weather during the daytime. Light clothing, sunglasses and sun protection should work well, but anyone remaining outdoors after sunset will again want a warmer layer as temperatures fall into the single digits.
Weather Trivia
Thunder Bay’s normal temperature for this point in August is approximately a daytime high of 23°C and an overnight low of 9°C.
That puts Saturday’s forecast high of 23°C almost exactly on the seasonal normal, while Sunday’s 22°C will be just slightly cooler.
The nights tell another late-summer story. Saturday night’s forecast low of 8°C and Sunday’s 9°C are reminders that even when afternoons still feel like summer, Northwestern Ontario nights are increasingly showing signs of the approaching change of season.
Source: Environment and Climate Change Canada observations from Thunder Bay Airport and the public forecast issued at 5:30 AM EDT Friday, August 21, 2026. Forecast details may change during the weekend, particularly the timing and coverage of Saturday’s showers.
