Southwestern Ontario under heat warning as region hit by season’s first hot spell

Hot, humid weather is set to blanket southwestern Ontario today as the region deals with its first hot spell of the season on a long weekend known for outdoor celebrations.

Environment and Climate Change Canada has issued a yellow heat warning for a stretch of the province spanning Windsor and the Niagara Region, up to Collingwood and the Greater Toronto Area.

The agency says temperatures are expected to soar starting this afternoon through Tuesday night, with daytime highs near 30 C or 36 C with humidex in some areas.

It says people should plan outdoor activities during the coolest parts of the day, limit direct exposure to the sun and heat, and make sure to drink water often.

Environment Canada says to watch for the early signs of heat exhaustion, such as headache, nausea and dizziness, and to call 911 if someone is showing signs of heat stroke, which can include red and hot skin as well as changes in consciousness.

In Toronto, the city says it is extending hours at the Scarborough, Etobicoke, North York and East York civic centres as well as Metro Hall so that people can go cool down.

The city says it is also freeing up an additional 112 shelter spaces for those experiencing homelessness and offering a 24-hour cooling spot on Spadina Road as long as the heat warning is in effect.

This report by The Canadian Press was first published May 18, 2026.

The Canadian Press