Sunshine Today, But Showers and Cooler Days Ahead for the Lakehead

THUNDER BAY – WEATHER REPORT – While much of Northwestern Ontario continues to battle extreme heat, Thunder Bay is proving once again that life beside Lake Superior comes with built-in climate control. This morning’s cool 4°C start is a refreshing reminder that spring is a slow dance along the north shore—especially with the big lake keeping its icy grip on the city’s weather.

Lake Superior’s Chill Keeps Things Comfortable Today, But Soggier Weather Looms Midweek

At 7:00 AM EDT, it’s a crisp 3.7°C at Thunder Bay Airport, with sunny skies stretching overhead. The dew point is a close 3.4°C, resulting in 98% humidity—expect a bit of patchy morning mist in the lower-lying areas. Winds are a gentle 8 km/h from the southwest, while the barometric pressure holds at 101.0 kPa, signaling calm but short-lived stable conditions.

Today will be a real gem for sun lovers, with clear skies and a high climbing to a pleasant 24°C by the afternoon. It may feel balmy inland, but if you’re by the lake, expect the temperatures to stay several degrees cooler. The UV index, however, will rise to 8—very high—so don’t be fooled by the cool morning air; sun protection is essential.

Tonight will start clear before becoming partly cloudy after midnight, bringing a 30 percent chance of showers or drizzle into the overnight hours. Fog patches will also develop, and the low will settle at 7°C, keeping things on the damp side.

Wednesday will bring a mix of sun and cloud, with a 30 percent chance of showers or drizzle and lingering fog patches—classic Thunder Bay spring. The high will drop to a cooler 15°C, as the wind shifts and cooler air settles back in. The UV index remains high at 8, so even with clouds, it’s still a sun-smart day.

Wednesday night will see increasing cloudiness with a low of 8°C.

Thursday brings cloud cover and a 30 percent chance of showers, with the high dipping further to just 13°C—definitely a sweater day. The rain will become more organized Thursday night with a low of 9°C.

Friday will stay cloudy with a 40 percent chance of showers and a high of 16°C, continuing into Friday night with more drizzle and a low of 7°C.

What to Wear for the Bay’s Breezy, Changing Weather

Today is a day for layers. Start the morning with a sweater or light jacket, but be ready to peel it off by midday if you’re away from the lakeshore. If you’re along the water, expect the breeze to keep things on the cooler side even in the afternoon. And yes, the UV index is sneaky today—apply that sunscreen.

Historical Weather for May 13

Thunder Bay’s record high for this day is a warm 28.9°C, while the record low sits at -4.6°C. Today’s forecast high of 24°C sits comfortably within the average spring range, though the temperature whiplash between cool lake breezes and inland warmth will be on full display.

Thunder Bay Weather Trivia

Did you know? Thanks to Lake Superior’s influence, Thunder Bay often experiences some of the greatest temperature contrasts between downtown and areas just a few kilometres inland. While inland may hit 24°C today, Marina Park could feel 5 to 8 degrees cooler thanks to the icy breath of the big lake.