Environment Canada has issued a special weather statement for the GTA and much of southern Ontario, with the first major heat event of the season expected Monday.

The agency said daytime temperatures are expected to reach the low 30s, while overnight lows are expected to be around 20 C.

“These conditions pose a health risk when you are not used to the heat,” Environment Canada said in its statement.

The statement covers an area stretching from Oshawa to Windsor and includes Toronto and surrounding areas.

People are being advised to drink lots of cool liquids to stay hydrated, to dress appropriately for the weather and to try and stay in cool places for at least several hours of the day.

Environment Canada also issued a special air quality statement for the region due to the possibility of deteriorating air quality caused by high pollution levels Sunday.

“Hot and sunny conditions are expected to cause increasing ground-level ozone concentrations in the area,” the agency said.

However the air quality advisory was cancelled by around 9:30 p.m. Sunday night.

After a sunny and hot day, Toronto is expected to see an overnight low of 14 C. However a high of 32 C is expected in the city on Monday. Warm temperatures are expected to persist through the week, with highs between 23 C and 27 C forecast between Tuesday and Saturday.