THUNDER BAY – WEATHER – It feels a lot more like early May than mid July today. While there is smoke in the air, today will be much cooler.
Thunder Bay begins Friday under widespread wildfire smoke, reduced visibility and an Orange Air Quality Warning. Showers may briefly improve conditions during the day, but very poor air quality is expected to continue through much of the weekend.
Environment Canada reports that wildfire smoke from northwestern Ontario is affecting the city. Everyone should limit outdoor activity, while people at greater risk from smoke should avoid strenuous outdoor activity whenever possible.
Today’s Weather Overview
Current Conditions
As of 7:00 a.m. EDT on Friday, July 17, the temperature at Thunder Bay was 17.4°C. The dew point was 15.6°C, producing a humidity level of 89 per cent and a damp, hazy start to the day.
Winds were light from the east-northeast at 5 km/h. Barometric pressure was 101.6 kPa and falling, suggesting unsettled weather remains nearby.
Visibility was reduced to six kilometres because of smoke.
Friday will be mainly cloudy, with showers developing during the morning before changing to a 40 per cent chance of showers near noon. There is also a risk of a thunderstorm.
Rainfall amounts of 10 to 15 millimetres are possible. Widespread smoke will continue, and the daytime high will reach only 18°C.
The UV index will be 7, or high. UV protection is still recommended even with cloudy and smoky conditions.
Orange Air Quality Warning
The air quality warning has a high impact level and high forecast confidence.
Heavy wildfire smoke can affect everyone, regardless of age or health. Possible symptoms include irritated eyes, nose or throat, headaches and coughing. More serious symptoms can include wheezing, chest pain or a severe cough.
Residents should limit time outdoors and consider postponing sports, festivals and other strenuous outdoor activities. Windows and doors should be kept closed where possible.
A certified portable air cleaner or the highest-quality filter suitable for a home ventilation system can help reduce smoke particles indoors.
People who must go outside may reduce their exposure by wearing a properly fitted NIOSH-certified N95 respirator or equivalent mask. However, wearing a respirator does not completely remove the health risks associated with wildfire smoke.
Older adults, pregnant people, infants, young children, people with chronic medical conditions and outdoor workers should take extra precautions.
Anyone experiencing a medical emergency should seek immediate medical assistance.
Extended Weather Forecast
Thunder Bay will remain mainly cloudy tonight, with a 40 per cent chance of showers and a continuing risk of thunderstorms.
Local smoke will remain in the area. The overnight low will fall to 13°C.
Tomorrow’s Forecast
Saturday, July 18
Saturday will be much warmer, but widespread smoke will continue.
The temperature will climb to 26°C, with a humidex value of 27. Northerly winds will increase to 20 km/h, gusting to 40 km/h.
The UV index will again be 7, or high.
Saturday night will be clear but smoky, with a low of 12°C.
Sunday, July 19
Sunday will bring a mix of sun and cloud, along with a 30 per cent chance of showers.
The daytime high will reach 26°C.
Cloudy periods and a 40 per cent chance of showers are expected Sunday night. The overnight low will be 17°C.
Monday, July 20
Monday will remain warm and unsettled, with a 40 per cent chance of showers during both the day and evening.
The daytime high will reach 26°C, followed by an overnight low of 15°C.
Wardrobe Recommendations
A light rain jacket and waterproof footwear will be useful Friday because of the potential for showers and thunderstorms.
People spending time outdoors should consider carrying an umbrella, although umbrellas should not be used when lightning is nearby.
An N95 or equivalent respirator may help reduce exposure to fine smoke particles when outdoor activity cannot be avoided.
Saturday and Sunday will be considerably warmer. Lightweight, breathable clothing will be more comfortable, but residents should continue to limit outdoor activity because of the smoke.
Sunglasses, sunscreen and a hat are recommended because the UV index will remain high.
Weather Trivia
Lake Superior can strongly influence Thunder Bay’s weather. Because the lake warms and cools more slowly than the surrounding land, temperatures near the shoreline can be noticeably cooler during warm summer afternoons.
The lake can also contribute to sudden changes in wind direction, cloud cover and visibility.
Source: Environment Canada forecast and air quality warning issued Friday, July 17, 2026.
Summary: Thunder Bay’s July 17 forecast calls for wildfire smoke, poor air quality, showers and possible thunderstorms. An Orange Air Quality Warning remains in effect, with warmer temperatures expected this weekend.
