Mostly cloudy skies hit Thunder Bay on Saturday , with light morning showers possible . The lake keeps shoreline temps cool while clouds stick around. By Sunday, sun takes over as inland heat grows . waterside breeze lingers than inland areas warm faster. 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.