Heat warning issued for Victoria Day with humidex expected to reach 36

A paddleboarder gets relief during the heatwave in Simcoe County. Tue., July 15, 2025. CTV NEWS/BARRIE/LUKE SIMARD

The first heat event of the spring is officially upon us, as the hot weather in the forecast for Victoria Day Monday has triggered a yellow heat warning from Environment Canada.

According to the weather agency, daytime highs could reach 30 degrees Monday afternoon with humidex values near 36. Overnight lows are expected to remain above 18 degrees.

The warning applies from central and southern Simcoe County, including Barrie, to the Greater Toronto Area, and from the Niagara Region through the Highway 401/403 corridor to Windsor.

The conditions are expected to ease by Tuesday night.

Safety messaging

Environment Canada urges protective action, particularly with those who may be more vulnerable, such as seniors or children.

“Watch for the early signs of heat exhaustion in yourself and others. Signs may include headache, nausea, dizziness, thirst, dark urine and intense fatigue. Stop your activity and drink water,” advised the weather agency in its warning. “Heat stroke is a medical emergency. Call 911 or your emergency health provider if you, or someone around you, is showing signs of heat stroke, which can include red and hot skin, dizziness, nausea, confusion and change in consciousness.”

Other recommended measures include staying hydrated, closing blinds or shades, cranking up the air conditioning, moving to a cooler space if needed, and planning outdoor activities during cooler parts of the day.

“Never leave people, especially children, or pets inside a parked vehicle,” added Environment Canada. “Check the vehicle before locking to make sure no one is left behind.”