Monday may not be the best day to go for a run or take part in any other strenuous activity.
Environment Canada has issued a special weather statement for Windsor, Leamington, and Essex County.
That is in addition to an existing heat warning.
The hot and humid conditions will mix with high levels of air pollution, creating ground-level ozone.
The agency said the risk is moderate throughout the day, but it could spike to high risk in the afternoon heat.
The air quality could cause symptoms like coughing, throat irritation, headaches or shortness of breath. Children, seniors, and those with cardiovascular or lung diseases like asthma are especially at risk.
The high on Monday is expected to reach 33 C or 27 C near Lake Erie, but with the humidity, it will feel like 40 C. On Tuesday, the humidex is expected to reach 41 C.