Summer is hitting the city early: Environment Canada has announced that the first major heat event of the summer is coming Monday.

Temperatures could be as high as 32 C in Toronto on Monday, with a humidex of 37 and a very high UV index of 9, caused by a warm and humid air mass moving into southern Ontario throughout the day. The sudden spike in temperatures could be risky for those unused to the heat, and the weather agency is advising people to drink plenty of water even before thirst is felt, to dress for the weather and to make sure to spend at least a few hours each day in a cool place.

This is the second special weather statement the current warm spell has inspired: Environment Canada put out a special air-quality statement Sunday morning warning of possible high levels of air pollution throughout southwestern Ontario for Sunday and possibly carrying into Monday.

The weather agency says the hot and sunny conditions are expected to cause increasing ground-level ozone concentrations in the area. According to the Ministry of Environment and Climate Change’s website, ground-level ozone results from chemical reactions by volatile organic compounds in the presence of sunlight. The colourless, odourless gas produced is a major component of smog, and causes irritation to the respiratory tract and eyes.

Read more: Expect more hot, sunny weather in Toronto this week

The air quality statement is put out whenever the Air Quality Health Index warns of high levels.

Environment Canada says air pollution could cause individuals to feel increased shortening of breath, light-headedness, throat irritation, headaches and experience coughing as a result. Children, seniors, and people with pre-existing health conditions — particularly ones involving the respiratory system — are at an increased risk.

The heat and the possibility of air pollution doesn’t mean you can’t go outside, but if you begin to experience any negative symptoms, health officials advise rescheduling strenuous outdoor plans and staying inside.

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