Thunder Bay weather update: June ends with the first heat event of the season as July begins hot and humid
Thunder Bay – WEATHER DESK – Thunder Bay is about to shift from a long, slow spring and a hesitant start to summer into the first major heat event of the season. It may not feel especially hot right now, but the weather service says hotter and more humid air is on the way as June closes and July begins.
A moderate-impact heat event is expected to begin Tuesday and continue through Friday, with the hottest conditions forecast from Tuesday through Thursday. Forecast confidence is high.
Heat Alert Overview
What to Expect
Thunder Bay can expect daytime highs between 29°C and 32°C, with some locations possibly reaching 33°C during the hottest stretch.
Overnight lows will remain warm, generally between 16°C and 19°C, with some nights possibly only dropping to 18°C to 22°C. That means there may be little relief from the heat, especially in homes without air conditioning.
Humidex values are expected to climb into the 36 to 41 range, making conditions feel much hotter than the actual temperature.
Timing
Tuesday Through Friday
The first heat event of the season begins Tuesday and is expected to last through Friday.
The most uncomfortable days are expected to be Tuesday, Wednesday, and Thursday, when both temperature and humidity will be at their highest.
Air Quality Concerns
Hot and humid air can also lead to deteriorating air quality. The Air Quality Health Index could approach the high-risk category, especially during the peak of the heat event.
People with breathing issues, heart conditions, seniors, children, outdoor workers, and anyone doing strenuous activity should take extra care.
Health and Safety Advice
Extreme heat can affect everyone’s health. Thunder Bay residents are urged to check on older adults, people living alone, young children, people with chronic health conditions, and others who may be more vulnerable.
Watch for early signs of heat exhaustion, including:
Headache, nausea, dizziness, thirst, dark urine, and intense fatigue.
If these symptoms appear, stop activity, move to a cooler place, and drink water.
Heat Stroke is a Medical Emergency
Call 9-1-1 immediately if someone shows signs of heat stroke, including:
Red and hot skin, confusion, dizziness, nausea, or a change in consciousness.
While waiting for medical help, move the person to a cooler place, remove extra clothing, and cool them with cold water or ice packs.
Staying Cool
Drink water often, even before you feel thirsty. Close blinds or shades during the hottest part of the day, and open windows only when it is cooler outside than inside.
Use air conditioning where available. If your home becomes too hot, move to a cooler public space such as a cooling centre, community centre, library, mall, or shaded park.
Plan outdoor work, exercise, and errands for the coolest parts of the day. Wear lightweight, light-coloured, loose-fitting clothing and a wide-brimmed hat.
Never leave children, vulnerable people, or pets inside a parked vehicle. Always check the vehicle before locking it.
Weather Outlook
Thunder Bay’s warmup comes after a cool and slow start to the season, but the arrival of July will bring a much more summer-like pattern. With highs near or above 30°C, elevated humidity, and warm nights, residents should prepare for several days of uncomfortable heat.
Continue to monitor updated forecasts and alerts from Environment Canada. Severe weather reports can be sent by email to ONstorm@ec.gc.ca or posted on X using #ONStorm.
