Thunder Bay weather for June 20, 2026: Mostly cloudy and cool at 10.5°C, with showers, a thunderstorm risk, a high of 19°C, and more unsettled weather into Sunday and Monday.
THUNDER BAY – WEATHER – Thunder Bay starts this Saturday under mostly cloudy skies with a damp, cool feel in the air. As of 7:00 AM EDT, the temperature is 10.5°C, with humidity sitting high at 92 percent and a light southwest wind at 8 km/h. The barometric pressure is 101.2 kPa and falling, pointing to unsettled weather ahead.
Environment Canada’s forecast calls for a cloudy day with showers developing this morning and a risk of a thunderstorm this afternoon. The daytime high is expected to reach 19°C, with a UV index of 3, or moderate.
Today’s Weather Overview
Current Conditions
It is a cool and moist start across Thunder Bay. The dew point is 9.3°C, close to the air temperature, which gives the morning a damp June feel. Visibility remains good at 24 kilometres, so travel conditions are generally manageable, though showers may reduce visibility at times later today.
Expect cloudy skies to dominate, with a 40 percent chance of showers early this morning, followed by a few showers beginning later in the morning. The main weather concern is the risk of a thunderstorm this afternoon, especially if daytime heating adds energy to the already unsettled air.
Tomorrow’s Forecast
Expected Conditions
Tonight: A few showers will end this evening, then skies become partly cloudy with a 40 percent chance of showers. There is still a risk of a thunderstorm early this evening. The overnight low will fall to 8°C.
Sunday, June 21: A mix of sun and cloud is expected, along with a 40 percent chance of showers. There is also a risk of a thunderstorm in the afternoon. The high will reach 20°C, and the UV index climbs to 7, or high, so sun protection will matter during brighter breaks. Sunday night will bring cloudy periods and a low of 6°C.
Monday, June 22: Thunder Bay gets a slightly warmer day, with a mix of sun and cloud and a 30 percent chance of showers. The high will rise to 23°C, before cloudy periods return Monday night with a low of 8°C.
Wardrobe Recommendations
A light rain jacket or water-resistant shell is the best choice today. Temperatures will be cool through the morning and only mild by afternoon, so a hoodie or light sweater underneath will help if you are heading out early.
Keep an umbrella handy, but be cautious using one during any thunderstorm activity. For Sunday, add sunscreen and sunglasses to the mix, as the UV index is expected to be high despite the chance of showers.
Weather Trivia
Thunder Bay’s weather is strongly influenced by nearby Lake Superior. In late spring and early summer, the lake is still relatively cool, which can help keep lakeshore temperatures lower than areas farther inland. That cooling influence can also contribute to shifting winds and changing cloud patterns during unsettled weather days.
