Thunder Bay weather for June 1, 2026: Mainly sunny and cool at 5.3°C this morning, warming to 18°C with very high UV
THUNDER BAY – WEATHER – Thunder Bay is starting June with a crisp, mainly sunny morning and very light winds. The day will warm steadily to a pleasant 18°C, but the bigger weather note comes tonight, when clear skies will allow temperatures to drop to 3°C with a risk of frost.
Today’s Weather Overview
Current Conditions
At 7:00 AM EDT Monday, June 1, 2026, conditions in Thunder Bay were mainly sunny with a temperature of 5.3°C.
The morning air is cool and damp, with a dew point of 3.9°C and humidity at 91 percent. Winds are very light from the west at 3 km/h, visibility is excellent at 32 km, and the barometric pressure is 102.1 kPa and rising.
Today will be sunny, with winds becoming east at 20 km/h this afternoon. The high will reach 18°C, and the UV index will be 8, or very high, so sun protection will still matter despite the cool start.
Tomorrow’s Forecast
Expected Conditions
Tonight: Clear skies will allow temperatures to fall quickly. The overnight low will be 3°C, with a risk of frost, especially in low-lying and sheltered areas.
Tuesday, June 2: Sunshine continues with a warmer high of 22°C. The UV index will be 7, or high. Tuesday night will remain clear, with a low of 7°C.
Wednesday, June 3: A warmer and slightly unsettled pattern begins. Expect a mix of sun and cloud with a 30 percent chance of showers and a high of 26°C. Wednesday night will bring cloudy periods with a 60 percent chance of showers and a low of 11°C.
Thursday, June 4: The chance of showers increases. Thunder Bay can expect a mix of sun and cloud with a 60 percent chance of showers and a high of 23°C. Thursday night will bring cloudy periods with a 40 percent chance of showersand a low of 12°C.
Wardrobe Recommendations
Start the day with a warm layer, such as a jacket or sweater, as temperatures are near 5°C early this morning. By afternoon, lighter spring clothing will be comfortable, but the east wind may keep it feeling cooler near Lake Superior.
For tonight, gardeners should take precautions because of the risk of frost. Cover sensitive plants, move containers to sheltered areas, and protect early-season flowers and vegetables.
Sunglasses, sunscreen, and a hat are recommended today because the UV index is very high.
Weather Trivia
Thunder Bay can still see frost risks into early June, especially under clear skies and light winds. These conditions allow heat to escape quickly after sunset, causing temperatures near the ground to drop faster than the official air temperature.
