Thunder Bay residents can look forward to comfortable, clear conditions this week, according to Environment Canada. As of 3:06 p.m. on Monday, August 24, 2026, the city was sitting at 22.7°C under partly cloudy skies, with a humidex of 24 and a gentle south wind.
The forecast for the rest of Monday calls for sunny skies and a high of 23°C, with a humidex of 25. The UV index is expected to reach 6, which Environment Canada rates as high. Tonight will be clear early, then partly cloudy near midnight, with an overnight low of 9°C.
No weather alerts are currently in effect for Thunder Bay. The current humidex falls in the ‘little discomfort’ range, meaning most people can go about their outdoor plans without heat-related concerns. This is a marked change from earlier in the summer, when an Orange Heat Warning in mid-July brought humidex values as high as 39 and smoky conditions from regional wildfires.
Looking ahead, Tuesday brings a 60 percent chance of showers and a risk of thunderstorms, with a cooler high of 18°C. Wednesday and Thursday both carry a chance of showers, but Friday through Sunday look mostly dry and pleasant, with highs ranging from 20°C to 22°C and overnight lows between 7°C and 14°C.
For comparison, the typical late-August high in Thunder Bay is around 22°C, with a low of 9°C. August is usually one of the wetter months, averaging about 15 rainy days and more than 130 mm of precipitation. This week’s mixed forecast fits that pattern, but the mild temperatures and lack of alerts mean residents can enjoy the outdoors with minimal disruptions.
