THUNDER BAY – WEATHER – Thunder Bay wakes up under gray skies, misty air, and persistent drizzle this Sunday morning. Today’s Weather OverviewCurrent ConditionsAs of 8:00 AM EDT from Thunder Bay Airport, it’s 15°C with light drizzle falling steadily. Extended Thunder Bay Weather ForecastSunday, September 21:Light drizzle through the morning, tapering to cloudy periods by the afternoon. Night: Clear skies, low around 11°C. Interestingly, Thunder Bay averages more fog in September than in May, and these foggy conditions often linger into the morning, especially after clear nights or light overnight rainfall.