Possible high levels of air pollution in the region prompted a special air quality statement from Environment Canada Tuesday.
It covered Windsor-Essex and Chatham-Kent, but it was lifted late Tuesday night.
"Hot and sunny conditions could cause increasing ground-level ozone concentrations this afternoon," the weather agency says.
Weather Services Specialist Etienne Gregoire adds the high temperature isn't the only factor affecting air pollution.
"It has to do a lot with the stability of the atmosphere, and how the pollutants get concentrated in the low level of the atmosphere. Warm temperatures don't necessarily equal a statement," says Gregoire.
People may experience coughing, throat irritation, headaches or shortness of breath. Kids, seniors and those with things such as asthma are especially at risk. Exposure to poor air quality is also a concern for people with heart or breathing problems and those with diabetes.
Environment Canada says if you experience any of these symptoms, consider stopping outdoor activities.