Environment Canada has issued a heat warning for Waterloo Region and Southern Wellington County.

The event is expected to begin Thursday and end Sunday, but could go early into next week as well.

The agency anticipates daytime high temperatures in the low thirties, with overnight lows near 20 degrees.

Hot and humid air is also expected in the coming days as well.

Environment Canada says residents should watch for symptoms like dizziness, fainting, nausea, vomiting, rapid breathing and heartbeat, and extreme thirst.

Risks are greater for young children, pregnant women, older adults, people with chronic illnesses and people working or exercising outdoors.