Cool Start Gives Way to Sunshine and a Week of Warming Weather
Thunder Bay Begins the Day Cloudy and Cool – But Brighter Skies Are on the Way
THUNDER BAY – WEATHER – Sunday, May 25, 2025 – Thunder Bay is off to a crisp, misty start this morning, with mostly cloudy skies and 100% humidity putting a soft veil over the Sleeping Giant. But don’t let the grey fool you—the sun is set to make its presence felt later today, kicking off a pleasant spring week along the shores of Lake Superior.
At 7:00 AM EDT, observations from the Thunder Bay Airport report a temperature of 5.3°C, with the dew point matching at 5.3°C—meaning the air is saturated and fog is not far behind. Winds are light out of the west-southwest at 6 km/h, visibility is a strong 32 km, and barometric pressure is rising at 102.8 kPa, a sign of continued fair weather.
Today’s forecast promises a mix of sun and cloud, with temperatures warming to a comfortable high of 17°C. The UV index is 6, rated as high, so if the sun peeks through, it’s time for that sunscreen.
Tonight, skies will clear and fog patches are expected to develop overnight, with temperatures dipping to a low of +4°C—a cool but typical May night.
A Gorgeous Start to the Week
Monday brings nothing but sunshine, with early morning fog patches clearing out to reveal a bright, warm day with a high of 20°C and a UV index of 7—definitely patio weather. Monday night remains clear and calm, with a low of 6°C.
Tuesday takes a slight detour from the sunshine with cloudy skies and a high of 18°C, while Tuesday night stays overcast with a low of 8°C.
Despite the clouds on Tuesday, the start of the week is looking solid—mild temperatures, manageable humidity, and a far cry from the unpredictable spring we’ve recently endured.
Wardrobe Suggestion
It’s a layer-up kind of morning. A light jacket or sweater will do the trick until the sun warms things up by mid-day. Don’t forget the sunglasses—despite the cloud cover, UV levels are high enough to matter.
Weather Trivia: Foggy Fame
Did you know? Thunder Bay’s Harbour is no stranger to fog, thanks to the chilly waters of Lake Superior meeting warmer spring air. It’s so common that early 20th-century ships were required to have foghorns in working order before entering the bay—an eerie, yet iconic sound of the city’s maritime past.
