July 22, 2025: Thunder Bay Detailed Weather Forecast

Thunder Bay – Weather – It’s a cloudy and humid morning in Thunder Bay, with mild temperatures expected to climb quickly under thickening cloud cover. A 40% chance of showers this afternoon could develop into thunderstorms later today, part of a larger weather pattern pushing warmer, moisture-laden air into northwestern Ontario. Conditions will feel significantly hotter, with a humidex of 31 expected by late afternoon.

Today’s Weather Overview

Current Conditions

At 7:00 AM EDT, the temperature at Thunder Bay Airport is 15.9°C, with cloudy skies and light northeast winds at 10 km/h. Humidity is sitting high at 87%, with a dew point of 13.7°C, indicating a moist atmosphere. Visibility is excellent at 32 km, and the barometric pressure is 101.6 kPa and falling, suggesting unsettled weather is on the way.

This afternoon, expect skies to remain mainly cloudy, with a 40% chance of showers and a risk of thunderstorms, especially in the early evening. Winds will shift from the northeast to south at 20 km/h late in the day. The high will climb to 25°C, with a humidex of 31, making it feel warmer than the actual temperature. The UV index is 8, rated very high, so sun protection is essential during any breaks in the clouds.

Tomorrow’s Forecast

Expected Conditions

Wednesday, July 23

• Day: Overcast and unsettled, with a 60% chance of showers and a risk of thunderstorms. It will be another warm day with a high of 23°C and a humidex of 32. UV index will drop to 3 (moderate) due to cloud cover.

• Night: Continued cloudiness, with a 30% chance of lingering showers. Overnight low of 15°C.

Thursday, July 24

• Day: A mix of sun and cloud, with a 30% chance of afternoon showers. The high will be 24°C.

• Night: Partly cloudy, with a 30% chance of showers. Low near 13°C.

Friday, July 25

• Day: A brighter day with a mix of sun and cloud and a more stable high of 25°C.

• Night: Cloudy periods continue. Low remains near 13°C.

Wardrobe Recommendations

• Today: Prepare for warm and muggy conditions — breathable summer wear is key. Be ready for rain or storms with a light waterproof jacket or umbrella, especially for evening plans. Sunscreen, sunglasses, and a hat are must-haves due to the very high UV index.

• Wednesday to Friday: Continue with light layers and be weather-aware for showers or storms, particularly Wednesday. A light sweater or jacket may be needed for cooler evenings later in the week.

Weather Trivia

Did You Know?
Thunder Bay often experiences lake-influenced weather, especially when northeast or southerly winds interact with Lake Superior. This can enhance moisture levels and fuel thunderstorms, particularly on warm summer days with a falling pressure system like today.