Mostly cloudy skies hit Thunder Bay on Saturday , with light morning showers possible . The lake keeps shoreline temps cool while clouds stick around. Sunday brings sharp sun breaks inland. Lake air stays cooler longer than spots farther from the water . Monday brings sharp temp jumps as the heat wave peaks away from Superior. waterside stays mild while inland spots bake. Local forecasters issued this outlook on July 12, 2026. A sunny Sunday follows the week’s damp start.